10 Surgical Procedures



10.1055/b-0039-171772

10 Surgical Procedures



10.1 Pterional (Frontotemporal Craniotomy)



10.1.1 Basic Information (Table 10.1a)























Indications




  • Aneurysms (anterior circulation + basilar tip and superior cerebellar artery)



  • Tumors:




    • Extra-axial: in sphenoid, parasellar, cavernous sinus, anterior + middle fossa



    • Intra-axial: insula, lateral frontal/parietal/temporal areas



  • Perisylvian AVMs



  • Hematoma evacuation in lateral frontal/parietal/temporal areas



  • “Workhorse exposure” for most procedures


Contraindications




  • Sellar/parasellar tumors:




    • In midline (prefer transsphenoidal approach)



    • With superoanterior extension (prefer bifrontal craniotomy)



  • Aneurysms:




    • Distal aneurysms of anterior cerebral artery



    • High-riding basilar aneurysms


Positioning




  • Patient position:




    • Supine



    • Ipsilateral shoulder up



  • Mayfield clamp:




    • Posterior paired pins → ipsilateral retromastoid region (equator)



    • Anterior single pin → contralateral frontal bone (midpupillary line)



  • Head (aim: malar eminence at highest point)




    • Elevation: above heart level



    • Rotation: contralateral 30–60 degrees



    • Neck extension: vertex down 10–30 degrees (allows gravity to retract frontal lobe away from anterior fossa floor)


!! Caution: make sure neck is free, no venous compression


Incision




  • Curvilinear




    • Starts: 1 cm anterior to tragus at zygomatic root (some prefer incision more posterior for cosmesis)



    • Course: up to linea temporalis → then anteriorly–superiorly



    • Ends: midline behind hairline (if widow’s peak present may get lower OR extend further contralaterally to midpupillary line)

Abbreviation: AVMs, arteriovenous malformations.



10.1.2 Key Procedural Steps (Table 10.1b)






































1. Skin elevation




  • From midline – linea temporalis: cut down to the bone—elevate scalp



  • From linea temporalis – zygoma root: dissect scalp from temporal fascia and elevate scalp separating from temporalis muscle up to the superficial fat pad (frontal branch of superficial temporal artery (STA) may serve as a landmark)


2. Preservation of frontalis branch of CN VII




  • Subfascial technique: incision of temporal fascia posterior to the superficial fat pad (stay 1 fingerbreadth behind fat pad) → in order to avoid injury to frontalis branch of CN VII, dissect temporalis fascia by staying in the plane right above the muscle→ reflect fat pad with scalp anteriorly 1 , 2



  • Use blunt dissection with bipolar coagulation for hemostasis, not monopolar cautery.


!! In the main author’s opinion, although this is the bloodiest plane of dissection it is also the safest in order to avoid injury to the frontalis branch of the facial nerve.


3. Temporalis muscle elevation




  • Muscle incision: from root of zygoma along the skin incision up to superior temporal line→ anteriorly along the superior temporal line (leave muscle cuff by incising muscle 1 cm below superior temporal line)



  • Subperiosteal muscle dissection: blunt dissection from inferior to superior to avoid injury to neurovascular supply of temporalis and atrophy



  • Muscle reflection anteriorly–inferiorly


4. Burr holes




  • McCarty keyhole*(= just above frontosphenoidal suture and behind frontozygomatic suture) 3 , 4



  • Above zygoma root*



  • Inferior to superior temporal line in line to zygoma root



  • Anterior to coronal suture



  • Above orbit (!! avoid frontal sinus, study pre-op CT → if frontal sinus is large, harvest pericranial flap before scalp elevation)


!! Variable placement of burr holes depending on surgeon’s preference and location of lesion. Burr holes with asterisk represent the essential ones.


5. Craniotomy




  • Drill trough between key hole – root of zygoma burr hole



  • Connect rest of burr holes with craniotome



  • Bone flap elevation


6. Further bone removal




  • Inferior part of temporal bone → remove bone down to middle fossa floor (!! beware of bone air cells)



  • Connection of anterior–middle fossa (anterior cranial fossa floor should be flush with middle cranial fossa floor)




    • Flatten orbital roof



    • Remove lesser wing of sphenoid bone (as flat as possible) upto lateral edge of superi-or orbital fissure (meaning orbital artery)


7. Dural opening




  • Dural tacking sutures



  • Semicircular flap (start incision from frontal dura) → reflect anteriorly (base at sphenoid bone)


8. Anterior clinoidectomy (intradural or extradural) (as needed)


Intradural clinoidectomy: semilunar incision of dura covering anterior clinoid process (ACP) with the base over optic nerve → strip dural flap away from ACP → drilling of ACP within the confines of cortical bone→ fracture gently and remove ACP → resect optic strut → open falciform ligament to mobilize optic nerve (see also ▶Fig. 9.3)


9. Sylvian fissure dissection




  • “Divide plane deep to superficial” like peeling an orange



  • Dissect Sylvian fissure along the frontal side of superficial Sylvian veins → mobilize these veins to the temporal side of the Sylvian fissure



  • May use cotton balls or retractors to help maintain fissure opening



  • Veins crossing the Sylvian fissure can be sacrificed


10. Closure




  • Watertight dura closure + central tack-up suture



  • Bone flap fixation (cover any bone defects with mesh or cement, if needed)



  • Temporalis muscle suturing



  • Galea sutures



  • Skin sutures



10.1.3 Pearls for Each Procedural Step (Table 10.1c)


















































Positioning


Head elevation + slight extension


Allows gravity to retract frontal lobe away from anterior fossa floor


Incision


Superficial temporal artery preservation (STA)




  • Technique: blunt dissection of scalp from superficial temporal fascia in the inferior part of the incision



  • Significance:




    • Sufficient blood supply of the skin flap (crucial in case of adjuvant radiotherapy, ensures good cosmetic outcome)



    • Could be used for bypass



    • Lower risk of post-op epidural hematoma due to STA bleeding


Do not extend incision below zygoma


Extending the incision below the zygoma increases the risk of facial nerve and superficial temporal artery injury


Craniotomy + extra bone removal


Combination with other extensions (e.g., orbitozygomatic, anterior clinoidectomy)




  • ↑ exposure



  • ↑ angle



  • Minimal brain retraction



  • Makes deep tumors superficial


Large lesions




  • Remove more bone to avoid brain retraction



  • First devascularize tumor and then debulk


Inadvertend periorbital fat exposure


If periorbital fat gets exposed, cover with Gelfoam or use bipolar to shrink


Additional bony removal before dura opening




  • Extradurally flatten frontal fossa bony ridges



  • Drill off the sphenoid ridge down to the level of the lateral superior orbital fissure



  • If bleeding from middle meningeal artery, first completly expose and then cauterize vessel


Meningorbital artery cauterization


Meningorbital artery can be cauterized w/ bipolar and divided to obtain slightly more exposure


Beware of air cells in posterior portion of middle fossa


After craniotomy push wax into air cells rather than swipe wax across air cells


Dural opening


Dural flap




  • Initially cut away from Sylvian fissure (frontal dura)



  • Dissect bridging veins before dura elevation



  • Place wet patties over dura to avoid dehydration and shrinkage


Dural tack-up sutures


Place dural tack-up sutures as deep as possible to tent dura flush with skull base


Closure


Check for inadvertent frontal sinus opening


Strip mucosa → plug nasofrontal duct → cover with vascularized pericranium (see also technique in Table 10.4c)



10.1.4 Complications: Avoidance + Mx (Table 10.1d)
































Complications

Symptoms/consequences

Mx

Entry into frontal sinus




  • CSF rhinorrhea



  • Infection



  • Pneumocephalus

strip mucosa → plug nasofrontal duct → cover with vascularized pericranium (see also technique in Table 10.4c)


Entry into orbit


Intraorbital bleeding


  • Hemostasis



  • If periorbital fat gets exposed, cover with Gelfoam or use bipolar to shrink


Injury of frontalis branch of CN VII


Inability to raise ipsilateral eyebrow

Avoid by incising temporal fascia posterior to superficial fat pad during scalp elevation (see step 2 in Table 10.1b)


Retraction injuries to frontal or temporal lobe





  • Head elevation + slight extension (allows gravity to retract frontal lobe away from anterior fossa floor)



  • Use cotton balls for retraction


Other general craniotomy complications: post-op hematoma, neurovascular injury, infection, cerebral infarction, and seizures



10.2 Pterional with Orbitozygomatic Osteotomy



10.2.1 Basic Information (Table 10.2a)




















Indications




  • Tumors in the following areas:




    • Anterior cranial fossa



    • Orbit



    • Medial sphenoid wing



    • Sellar region (suprasellar, parasellar)



    • Anterior cavernous sinus



    • Middle cranial fossa



  • Aneurysms:




    • Acom



    • Paraclinoid ICA, opthalmic artery



    • Basilar apex aneurysms



    • Complex anterior circulation aneurysms


!! combination w/ posterior clinoidectomy and/or anterior petrosectomy allows access to upper clivus


Contraindications


Sellar/parasellar tumors with superoanterior extension (prefer bifrontal craniotomy)


Positioning




  • Patient position:




    • Supine



    • Ipsilateral shoulder up



  • Mayfield clamp:




    • Posterior paired pins → ipsilateral retromastoid area (equator)



    • Anterior single pin → contralateral frontal bone in midpupillary line (equator)



  • Head (aim: malar eminence at highest point)




    • Elevation: above heart



    • Rotation: contralaterally up to 30 degree



    • Neck extension: vertex down 10–30 degree (allows gravity to retract frontal lobe away from anterior fossa floor)


Incision


Variable, C-shaped (usually)




  • Starts: 1 cm anterior to tragus at zygomatic root



  • Course: up to linea temporalis → then anteriorly – superioriorly



  • Ends: contralateral midpupillary line behind widow’s peak



10.2.2 Key Procedural Steps (Table 10.2b)











































1. Skin elevation




  • From midline – linea temporalis → cut down to the bone – elevate scalp



  • From linea temporalis – zygoma root: dissect scalp from temporal fascia and elevate scalp separating from temporalis muscle up to the superficial fat pad (frontal branch of STA may serve as a landmark)


!! preserve STA if possible


2. Preservation of frontalis branch of CN VII




  • Incision of temporal fascia posterior to the superficial fat pad (stay 1 fingerbreadth behind fat pad) → in order to avoid injury to frontalis branch of CN VII, dissect temporalis fascia by staying in the plane right above the muscle (use blunt dissection with bipolar coagulation for hemostasis, not monopolar cautery)



  • At the junction of the fascia with the zygomatic arch, perform subperiosteal dissection releasing fascia from the top of the zygomatic arch



  • Subperiosteal exposure of frontozygomatic process



  • Reflect fat pad with scalp anteriorly


!! In the main author’s opinion, although this is the bloodiest plane of dissection it is also the safest in order to avoid injury to the frontalis branch of the facial nerve.


3. Cuts to zygomatic arch and temporalis muscle reflection




  • Perform osteotomy using reciprocating saw at the root of the zygoma and at junction of zygomatic arch with maxilla



  • Muscle incision: from root of zygoma along the skin incision up to superior temporal line → anteriorly along the superior temporal line (leave muscle cuff by incising muscle 1 cm below superior temporal line)



  • Subperiosteal muscle dissection: blunt dissection from inferior to superior to avoid injury to neurovascular supply of temporalis and atrophy



  • Reflect temporalis muscle inferiorly with zygomatic bar attached to the muscle


4. Frontotemporal craniotomy


see steps 4, 5 in Table 10.1b


5. Bone exposure for osteotomies


Dissect off bone:




  • Periorbita: from right above medial canthus through orbital roof → to right above lateral canthus



  • Frontal fossa intracranial dura: from the level of the falx (avoid injury to olfactory nerve) → all the way to the sphenoid ridge at the level of the lateral border of the superior orbital fissure, over the entire superior orbital roof



  • Temporal fossa intracranial dura: from the sphenoid ridge at the level of the lateral border of the superior orbital fissure posteriorly to the posterior margin of the frontotemporal craniotomy


6. Orbitozygomatic osteotomy


(see ▶Fig. 10.1)


  • Dissection of supraorbital neurovascular bundle: depending on whether frontal osteotomy will be medial or lateral to supraorbital notch dissect neurovascular bundle free from notch




  • Cut #1: vertical cut along orbital rim in the sagittal plane: with brain ribbons protecting the frontal dura and the periorbita, use reciprocating saw to make vertical cut along orbital rim lateral to supraorbital notch in the sagittal plane, which extends:




    • From intracranial space



    • Through orbital roof



    • Into orbital space




  • Cut #2: curved cut along orbital roof in the coronal plane: with brain ribbons protecting frontal dura, temporal dura, and periorbita, use reciprocating saw to perform perpendicular osteotomy in the coronal plane, that extends:




    • From the level of the previous frontal cut



    • Along orbital roof



    • 1 cm deep into sphenoid bone



    • Out into temporal fossa




  • Cut #3: horizontal cut along sphenoid bone – lateral orbital wall in the axial plane: with brain ribbons protecting temporal dura and lateral periorbita, use reciprocating saw to perform osteotomy that extends:




    • From temporal fossa



    • Into sphenoid bone at the level of the previous osteotomy



    • Into the orbit




  • Elevation of osteotomy flap: orbital rim should now be free and mobile. Use handheld osteotome to free it completely and elevate


8. Additional craniectomy


Use high-speed drill and rongeurs to remove additional bone as desired:




  • Squamous temporal bone (down to middle fossa floor)



  • Lesser sphenoid wing (unroofing of superior orbital fissure, no bone between globe – ACP)



  • Anterior clinoidectomy (see step 8 in Table 10.1b)



  • Unroofing of optic canal


9. Dural opening




  • C-shaped across Sylvian fissure (exposing half of frontal and temporal lobes)



  • Dural flap reflected anteriorly (also depressing gently periorbita – eye)


10. Closure




  • Watertight dura closure + central tack-up suture



  • Fixation of orbitozygomatic osteotomy



  • Bone flap fixation (cover any bone defects with mesh or cement)



  • Temporalis muscle suturing



  • Galea sutures



  • Skin sutures



10.2.3 Orbitozygomatic Osteotomy Cuts (▶Fig. 10.1)



10.2.4 Pearls for Each Procedural Step (Table 10.2c)






















Pre-op preparation


Assess size of frontal sinus in pre-op CT


If frontal sinus is large, the risk to be opened during craniotomy is higher → harvest pericranial flap before scalp elevation


Check for pneumatized ACP in pre-op CT


ACP may be pneumatized. In case of anterior clinoidectomy, this can be a route for CSF rhinorrhea. Try to not violate the mucosa during its removal. If there is a small violation, you may stitch, otherwise pack sphenoid with fat/muscle graft and place lumbar drain (LD)


Closure


Avoid extraocular muscle entrapment when replacing orbital osteotomy flap


While replacing the orbital flap there is a risk of extraocular muscles getting entrapped in bone gaps


Note: See also following pearls in frontotemporal craniotomy (also important for orbitozygomatic craniotomy):




  • Head elevation + slight extension



  • STA preservation



  • Inadvertent periorbital fat exposure



  • Beware of air cells in posterior portion of middle fossa



  • Check for inadvertent frontal sinus opening



10.2.5 Complications: Avoidance + Mx (Table 10.2d)
















































Complications

Risks

Avoidance/Mx

Injury of frontalis branch of CN VII


Inability to raise ipsilateral eyebrow


  • Avoid by incising temporal fascia posterior to superficial fat pad during scalp elevation (see Step 2 in Table 10.2b)



  • Avoid by placing incision at the root of the zygoma (not inferior)


Violation of periorbita




  • Injury of intraorbital contents



  • No visualization of reciprocating saw during orbitozygomatic (OZ) osteotomy


  • Avoid by carefully elevating periorbita off the orbital walls and protecting it at all time with brain ribbon during osteotomies



  • Hemostasis



  • If periorbital fat gets exposed, cover with Gelfoam or use bipolar to shrink


Injury of trochlear attachment of superior oblique muscle


Diplopia

Avoid periorbita dissection medial to supraorbital notch


Extraocular muscle entrapment when replacing orbital osteotomy flap


Diplopia

While replacing the orbital flap, check for extraocular muscles getting entrapped in bone gaps


Post-op pulsatile enopthalmos





  • Avoid by preserving lateral orbital wall



  • Usually resolves in 3–6 months


Eye injury


Vision disturbances

Avoid by keeping periorbita intact and protecting it at all time with brain ribbon during osteotomies


Entry into frontal sinus




  • CSF rhinorrhea



  • Infection



  • Pneumocephalus

Strip mucosa → plug nasofrontal duct → cover with vascularized pericranium (see also technique in Table 10.4c)


Retraction injuries to frontal or temporal lobe





  • Head elevation + slight extension (allows gravity to retract frontal lobe away from anterior fossa floor)



  • Use cotton balls for retraction



  • Remove more bone


Other general craniotomy complications: post-op hematoma, neurovascular injury, infection, cerebral infarction, and seizures



10.3 Transcallosal Approach



10.3.1 Basic Information (Table 10.3a)

























Indications


Exposure




  • In body of lateral ventricle



  • Anterior two-third of third ventricle


Tumors




  • Colloid cysts



  • AVM



  • Thalamic gliomas



  • Craniopharyngioma etc.


Contraindications




  • Lesion location in anterior frontal horn, posterior atrium, or temporal horn (prefer transcortical route)



  • Crossed dominance 5 :




    • Definition: different hemispheres control dominant hand and speech/language



    • Post-op writing/speech deficit in case of transcallosal approach


Positioning




  • Position:




    • Supine



    • Thorax elevation



  • Mayfield head holder



  • Head




    • Elevation: above heart level



    • Neutral position (helps surgeon stay oriented to midline)



    • Extension: 10 degree



  • Choose right-sided approach (preferrably)


Incision


Modified bicoronal incision




  • Shorter, centered to midline



  • 2–3 cm anterior to coronal suture



  • Anteroposterior skin flap retraction (exposure around 4 cm anterior and 2 cm posterior to coronal suture)



10.3.2 Key Procedural Steps (Table 10.3b)





























1. Anterior parasagittal craniotomy




  • Rectangular (size: AP)



  • Nondominant hemisphere (usually)



  • Extents:




    • Mediolateral extent: extending up to or encompassing midline (total width ≈ 4 cm)



    • Anteroposterior extent relative to coronal suture (two-third anterior + one-third posterior to coronal suture) (total length ≈ 5–6 cm)


!! Criterion: study pre-op magnetic resonance venography (MRV) for variations in draining veins




  • Craniotomy:




    • Drill a trough along sinus: using an M8 bit w/ the non-cutting tip pointing toward the sinus. Unroof the edge of the superior sagittal sinus (SSS) along its entire length where it abuts the planned craniotomy



    • Two burr holes at the lateral two corners of the planned craniotomy (optional)


Using a craniotome, complete the parasagittal craniotomy, always cutting away from sinus


2. Dural opening




  • “U”-shaped dural flap based on SSS → reflect over midline



  • Preserve draining veins while retracting dural flap


3. Interhemispheric dissection




  • Aims:




    • Minimal retraction (≤ 2 cm)



    • Avoid venous infarction (avoid too much retraction on sinus causing thrombus or occlusion)



  • Technique: combination of alternating sharp dissection + retractor blade advancement



  • Anatomical structures to identify before corpus callosum (CC) (from superficial to deep):




    • Inferior falx



    • Inferior sagittal sinus



    • Cingulate gyri



    • Callosomarginal arteries



    • Pericallosal arteries



  • CC features: pearly white, relatively avascular (see Chapter 9, ▶Fig. 9.5)


4. Callosotomy




  • Technique: split CC down the midline w/ bipolar cautery and suction (check pre-op imaging for midline asymmetry!) → widen opening (length < 2–3 cm) → advance retractor → side identification



  • Identification of side: choroid plexus (CP) courses medially to the thalamostriate vein (both structures if followed, guide surgeon to foramen of Monro [Fmo] (see Chapter 9, ▶Fig. 9.5)


! Always → fenestrate/excise septum pellucidum


!! Suspect entry into cavum septum pellucidum, if after opening CC no veins or CP is identified


!!! Make sure the trajectory of callosotomy is perpendicular to CC (ensures shorter route in CC)


5. Entry into body of lateral ventricle


Orientation:




  • Identify CP and trace it anteriorly up to the Fmo



  • CP is located medially to the thalamostriate vein


6. Approaches to third ventricle (if needed) (see Table 10.3c)




  • Selection criteria:




    • Lesion (size, location, and characteristics)



    • Avoidance of post-op deficits



  • Options:




    • Transforaminal



    • Transchoroidal (sub-/suprachoroidal)



    • Interforniceal


7. Closure




  • Irrigation of ventricular system to wash out clots



  • Inspect ventricular system for obstruction



  • Layer-by-layer hemostasis (esp. callosotomy, cortex)



  • Leave external ventricular drain (EVD) (hydrocephalus prevention)



  • Watertight dura closure



  • Bone flap fixation



  • Galea closure



  • Skin closure



10.3.3 Approaches into Third Ventricle (Table 10.3c)




















































Approach

Definition

Indications

Caution

Pros

Cons

Transforaminal


Through Fmo


  • Tumor location: anterior third ventricle



  • Tumor characteristics: cystic/soft



  • Tumor dilates FMo

Avoid further dilation of FMo (risk for memory deficit)

Uses a natural opening (no need for creating a new one) → least traumatic


Transchoroidal


Subchoroidal


Incision in taenia choroidea → CP retracted upward

Extra access to the middle and posterior third ventricle

Beware of venous tributaries to superior choroidal veins

Less risk for forniceal injury


  • May require unilateral thalamostriate vein sacrifice (neuro deficits)



  • May require sacrifice of venous tributaries from thalamus – basal ganglia


Suprachoroidal

Incision in taenia fornicis → CP deflected downward


Safer (preferred) → less manipulation of superficial caudate, thalamic veins

Risk of unilateral forniceal injury


Interforniceal


Between bodies of fornices by dividing the interforniceal raphe

↑morbidity → reserved only for tumors distending upward 3rd ventricle roof located in the posterior two-third of third ventricle (rarely used)

Hippocampal commissure (avoid extending incision to the posterior component of fornices)


Risk of bilateral forniceal damage → memory impairment

Note: See ▶Fig. 9.6



10.3.4 Pearls for Each Procedural Step (Table 10.3d)














































Pre-op preparation


Pt selection




  • Check for crossed dominance



  • Pre-op neuropsychological assessment in pts with cognitive impairment (esp. memory deficits)



  • Pre-op vascular anatomy study


Pre-op imaging study




  • MRV: find optimal surgical corridor between bridging veins



  • CC midline distortion



  • Beware of existence of cavum septum pellucidum


Transcortical approach (alternative)




  • Main author prefers transcortical approach in pts w/ hydrocephalus



  • There is higher risk of epilepsy but less cortical structures en route


Interhemispheric stage


Avoid venous infarction




  • Vein preservation



  • Do not retract the medial hemisphere surface > 2 cm



  • Maintain pt well hydrated during surgery


Interhemispheric dissection




  • Wait 2–3 min between every advancement of the retractor blade (allows for ventricular pressures to equilibrate)



  • Brain relaxation measures (mannitol, hyperventilation)


Do not mistake cingulate gyrus for CC


Below the falx and superior to CC, the two cingulate gyri may be adherent to each other and can be mistaken for CC. Identify CC by its bright white color and its relative hypovascularity (vs cingulate gyri, which are yellow white). Furthermore, pericallosal arteries lie on CC (see ▶Fig. 9.5)


Intraventricular stage


Preservation of anatomical structures




  • Draining cortical veins



  • Thalamostriate vein



  • Fornices


Control of tumor blood supply




  • CP tumors (papilloma, meningioma) → blood supply from choroidal arteries (ligate early)



  • Ependymal tumors (gliomas, neurocytomas etc) → blood supply from small ependymal vessels (require meticulous dissection)


Tumor dissection


Always maintain plane between tumor – ependyma


Closure


Hydrocephalus prevention


Place cottonoid into FMo to prevent blood from pooling into third ventricle


EVD


Always leave ventriculostomy post-op



10.3.5 Complications: Avoidance +Mx (Table 10.3e)
















































Complications

Consequences

Avoidance/Mx



  • Venous injury/obstruction



  • SSS injury/thrombosis




  • Venous infarcts



  • Hemiparesis



  • Brisk venous hemorrhage



  • Air embolism


  • Avoid by:




    • Preserving draining cortical veins (no sacrifice, less manipulation)



    • Minimizing midline retraction (≤ 2 cm)



    • Preserving thalamostriate vein



    • Keeping veins wet



    • Placing two-third of craniotomy anterior to coronal suture (minimal risk for cortical veins draining motor or supplementary motor cortex to cross the surgical field – usually drain into SSS 2–3 cm behind to coronal suture



    • Brain relaxation measures (mannitol, hyperventilation, CSF drainage after callosotomy)



    • Adequate hydration



  • Mx: see Table 11.1d


Transient akinetic mutism (range: slow speech initiation → mutism)

Other potential syndrome symptoms:




  • Paraparesis



  • Incontinence



  • Seizures



  • Emotional disturbances

Avoid by:




  • Limiting CC incision (1–2 cm)



  • Minimizing retraction to anterior cingulate gyrus, fornix (take brain relaxation measures, avoid using retractors, prefer cotton balls or rolled cottonoids for retraction of cingulate gyri



  • Preserving vessels of supplementary motor area, basal ganglia, thalamus


Disorders of interhemispheric information transfer




  • Disorder of visuospatial info transfer



  • Disorder of tactile info transfer



  • Bimanual learning difficulty



  • Alexia

Avoidance:




  • Limit CC incision (2–3 cm)



  • Avoid posterior callosotomy (splenium)


Unilateral thalamostriate vein injury/sacrifice




  • Hemiplegia



  • Drowsiness



  • Mutism

Avoidance:




  • Preserving vein



  • Preferring suprachoroidal over subchoroidal approach


Fornix injury


Amnesia (usually transient amnesia of recent events)

Avoidance:




  • Do not distend FMo in transforaminal approach



  • Preserve fornix



  • Avoid interforniceal approach


Obstructive hydrocephalus


Neurological deterioration


Coma

Avoidance:




  • Irrigate ventricles at closure



  • Hemostasis



  • Leave EVD



  • Placement of cottonoid patties into ventricles to prevent debris and blood clot dispersal – remove them at closure



  • Open septum pellucidum (prevents occurrence of trapped ventricle)


Injury of pericallosal artery injury of callosomarginal artery




  • Contralateral hemiparesis with lower limb predominance



  • Sensory deficits of contralateral limbs, urinary incontince



  • Akinetic mutism (infarction of left supplementary motor area)



  • Ideomotor apraxia (pericallosal)



  • Decreased verbal fluency



  • Abulia

Avoidance:




  • Meticulous dissection



  • Good knowledge of regional anatomy and the anatomical structures encountered



  • Do not mistake cingulate gyri for CC and callosomarginal arteries for pericallosal arteries, thus entering into cingulate gyri and injuring the pericallosal arteries


CSF leak




  • CSF leak from wound



  • Subgaleal CSF collection


  • Avoid with watertight dura closure



  • Mx with running-locking sutures oversewing leak (see Chapter 11: Complications, CSF leak)


Other general craniotomy complications: post-op hematoma, infection, cerebral infarction



10.3.6 Approaches to Ventricles


6 (Table 10.3f)













































Target

Approach

Lateral ventricles


Frontal horn (anteroinferior wall)




  • Anterior frontal via rostrum of CC


Body




  • Anterior transcallosal



  • Anterior transcortical via middle frontal gyrus


Atrium




  • Transcortical approaches




    • Posterior transcortical via superior parietal lobule



    • Transcortical via posterior middle/inferior temporal gyrus



    • Via isthmus of cingulate gyrus (occipital approach)



  • Posterior transcallosal (via posterior splenium)

Temporal horn

Transcortical via inferior part of middle temporal gyrus or superior part of inferior temporal gyrus (via temporal or posterior frontotemporal approach)


Occipital horn


Transcortical via isthmus of cingulate (gyrus occipital approach)


Third ventricle


Anterior

Midline approaches




  • Anterior transcallosal approach




    • Transforaminal approach



    • Transchoroidal (sub/suprachoroidal) approach



    • Interforniceal approach



  • Subfrontal approach:




    • Opticocarotid approach (through opticocarotid triangle)



    • Subchiasmatic approach (below optic chiasm between the optic nerves)



    • The lamina terminalis approach (through lamina terminalis)



    • Transfrontal – transsphenoidal (through planum sphenoidale – throughsphenoid sinus)



  • transsphenoidal approach


Lateral approaches




  • Posterior frontotemporal



  • Subtemporal


Posterior




  • Median/paramedian supracerebellar infratentorial



  • Posterior transcallosal



  • Occipital transtentorial



  • Posterior transcortical via superior parietal lobule


Fourth ventricle




  • Midline suboccipital approachTranscortical via vermis



  • Telovelar approach



10.4 Bifrontal Craniotomy With Supraorbital Bar Removal



10.4.1 Basic Information (Table 10.4a)


























Craniotomy


Indications


Bifrontal


Access to:




  • Entire anterior cranial fossa



  • Anterior midline parasellar area (tuberculum, ACom, ICA, chiasm, optic nerve)


Plus supraorbital bar removal




  • Smaller and more posterior lesions



  • Significant superior extension of lesions


! pros: ↓ retraction and ↑ visualization


Contraindications




  • Middle cranial fossa lesions



  • Sub-/retrochiasmatic lesions (prefer pterional or orbitozygomatic approach)



  • Paranasal sinus infection


Positioning




  • Patient position:




    • Supine



    • Thorax elevation



  • Mayfield clamp:




    • Paired pins: above mastoid in the coronal plane (push skin forward before fixating head to decrease tension on incision during closure



    • Single pin: above the contralateral pinna



  • Head (aim: ipsilateral orbital rim at highest point)




    • Elevation



    • Neutral position



    • Neck: slightly extended 10–15 degrees (allows gravity retraction)


Incision


Bicoronal skin incision




  • Starts: 1 cm anterior to tragus of one ear



  • Ends: 1 cm anterior to contralateral tragus


* In midline the incision forms an anteriorly directed peak



10.4.2 Key Procedural Steps (Table 10.4b)








































1. Soft-tissue elevation




  • Scalp elevated anteriorly over orbital rim



  • Subfascial reflection of fat pad containing frontalis branch of CN VII posterior to frontal process of zygomatic bone (see step 2 in Table 10.2b)



  • Rectangular piece of vascularized forehead pericranium reflected separately anteriorly as far as nasofrontal suture (keep wet)


2. Bifrontal craniotomy




  • Burr holes:




    • McCarty keyholes bilaterally



    • Drilling of bone over SSS near frontal fossa (anteriorly) and in front of coronal suture (posteriorly) → expose SSS and dura on each side of sinus



  • Bifrontal craniotomy (as close to the anterior cranial fossa as possible)


3. Further bony exposure for biorbitonasal osteotomy




  • Free supraorbital nerve from supraorbital notch/foramen (after opening it with osteotome/drill)



  • Elevate scalp upto nasofrontal suture



  • Frontal dura dissection: dissect frontal dura off frontal fossa and orbital roofs preserving attachments at the crista galli



  • Periorbita dissection: dissect periorbita bilaterally from medial to supraorbital notch to just above medial canthus


4. Biorbitonasal osteotomy (see ▶Fig. 10.2)


Cut #1: horizontal osteotomy above nasofrontal suture


With brain ribbons bilaterally protecting medial periorbita and frontal dura → perform horizontal osteotomy using reciprocating saw just above nasofrontal suture:




  • Starting in one orbit



  • Extending 1 cm deep into nasal bone (not deeper, in order to avoid crista)



  • Out into the other orbit


Cuts #2 and 3: vertical cuts along orbital rim in the sagittal plane


With brain ribbons bilaterally protecting the frontal lobe and the periorbita, → use reciprocating saw to make vertical cuts in the sagittal plane just medial to the supraorbital notches along orbital rim which extend:




  • From intracranial space



  • Through orbital roof



  • Into orbit


Cut#4: coronal cut along orbital roofs – nasal bone


With brain ribbons bilaterally protecting medial periorbita and frontal dura, perform perpendicular cut using reciprocating saw in the coronal plane that:




  • Starts from the level of the previous sagittal frontal cut (cut #2)



  • Along one orbital roof



  • Then 1 cm deep into nasal bone down to the level of the previous horizontal nasal osteotomy (cut #1), anterior to crista



  • Out into the contralateral orbit, along the orbital roof



  • To the level of the previous contralateral sagittal frontal cut (cut #3)


Elevation of osteotomy flap


Orbital rim should now be free and mobile. Use handheld osteotom to free it completely and elevate


5. Dura opening – division of SSS


b/l horizontal dural openings ligations (as close to anterior cranial fossa as possible) → b/l gentle retraction of frontal lobes away of falx → 2 SSS ligations (as close to anterior cranial fossa as possible) → division of SSS together with falx between the ligations


6. Intradural dissection


Depending on pathology


7. Closure




  • Frontal sinus closure (see also Table 10.4c: technique for preventing CSF rhinorrhea from frontal sinus)



  • Repair of anterior cranial fossa with vascularized pericranial flap




    • Cover frontal sinus (below orbital osteotomy piece)



    • Cover defects on anterior cranial fossa (below frontal lobes)



  • Dural closure: circumferentially sew dura to pericranial flap, which has replaced basal dura



  • Craniotomy – osteotomy bone flap fixation + possible cranioplasty



  • Galea closure



  • Skin closure



10.4.3 Biorbitonasal Osteotomy Cuts (▶Fig. 10.2)



10.4.4 Pearls for Each Procedural Step (Table 10.4c)
































Soft tissue elevation


Vascularized pericranium flap




  • Always harvest a vascularized pericranium flap → utilities:




    • Frontal sinus exclusion



    • Repair of anterior cranial fossa defects



    • Prevention of CSF rhinorrhea


! Caution: when replacing biorbital rim/frontal craniotomy over vascularized pericranial graft, beware not to strangulate the graft → this may lead to graft venous congestion and associated mass effect.


Dura dissection


Ethmoidal artery cauterization


Early anterior ethmoidal artery cauterization to devascularize anterior midline skull base tumors


Frontal fossa drilling


Before opening dura extradurally, use diamond drill:




  • To flatten frontal fossa bony ridges



  • To devascularize potential intradural lesion (such as olfactory groove meningioma) from ethmoidal feeders


Craniotomy


Drilling over SSS


Pros vs burr holes straddling SSS:




  • Better dura detachment for craniotomy → protection of bridging veins during craniotomy



  • Better SSS dissection → SSS protection during craniotomy – bone flap elevation


* Main author always drills bone over sinuses instead of burr holes for craniotomies involving sinuses


Osteotomy


Biorbitonasal osteotomy


Pros:




  • ↓ brain retraction



  • Low and flat trajectory for lesions located more posterior in anterior cranial fossa



  • Removes obstructions around lesser sphenoid wing


! Main author is very liberal with use of biorbitonasal osteotomies in order to decrease frontal lobe retraction, particularly for large bilateral lesions


Closure


Technique for preventing CSF rhinorrhea from frontal sinus




  • Strip mucosa (study frontal sinus drainage, beware of duplicate orbital roof)



  • Drill thin layer of bone from entire sinus wall (in order to ensure that all mucous secreting cells have been removed)



  • Plug nasofrontal duct with Gelfoam soaked with bacitracin ointment followed by muscle plug



  • Apply vascularized pericranium graft



10.4.5 Complications: Avoidance + Mx (Table 10.4d)




















































Complications

Consequences

Avoidance/Mx

Injury of frontalis branch of CN VII


Inability to raise ipsilateral eyebrow

Avoid by subfascial elevation of fat pad


Supraorbital nerve injury


Frontal numbness/pain

Avoid by freeing nerve from supraorbital notch/foramen during scalp elevation


Unilateral trochlear pulley injury


Diplopia

Avoid with careful dissection of periorbita from medial orbital roof


CSF rhinorrhea due to entry into frontal sinus




  • Infection



  • Pneumocephalus


  • Avoid by covering frontal sinus with pericranial flap (see Table 10.4c for technique)



  • Use lumbar drainage when indicated (for Mx, see Table 11.1f)


SSS injury




  • Brisk venous bleeding



  • Air embolism

Avoid by drilling trough parallel to sinus edge instead of burr holes across sinus → better SSS dissection (for Mx, see Table 11.1d)


Frontal lobe injury




  • Brain contusions



  • Edema



  • Neurological deterioration

Avoidance:




  • Minimal frontal lobe retraction



  • Slight head extension (allows gravity to retract frontal lobe away from anterior fossa floor)



  • Supraorbital bar removal minimizes need for retraction



  • Brain relaxation measures (mannitol, hyperventilation)


Post-op pulsatile enopthalmos





  • Usually resolves in 3–6 months


Eye injury


Vision disturbances

Avoid by keeping periorbita intact and protecting it at all time with brain ribbon during osteotomies


Olfactory nerve injury


Impaired olfaction


  • Avoid by preserving dural attachments at the crista galli during elevation of dura from frontal fossa and orbital roofs



  • Avoid with minimal retraction of frontal lobes


Other general craniotomy complications: post-op hematoma, neurovascular injury, infection, cerebral infarction, and seizures

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May 11, 2020 | Posted by in NEUROSURGERY | Comments Off on 10 Surgical Procedures

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