7 Functional Neurosurgery



10.1055/b-0039-171769

7 Functional Neurosurgery



7.1 Pain



7.1.1 Neuralgia (Table 7.1a)







































































Disease

Presentation

Diagnostics

Other

Treatment

Trigeminal neuralgia AKA Tic Douloureux




  • Paroxysmal, electric shooting character



  • Triggers: eating, talking, brushing teeth, touching nose, wind blowing on face



  • Most frequent: V2 + V3, followed by V2



  • Right > left



  • Almost always unilateral, only 1% bilateral (more common in multiple sclerosis [MS])



  • No neurologic deficit



  • Burning dysesthesia indicates permanent nerve injury

MRI/MRA brain to exclude tumor and MS


Causes:




  • Microvascular compression at trigeminal nerve root entry zone by:




    1. Superior cerebellar artery



    2. Branch of petrosal vein



    3. Ectatic basilar artery



    4. Persistent trigeminal artery



  • MS plaque



  • Tumor



  • Idiopathic

Trigeminal nuclei:




  1. Midbrain: proprioception



  2. Pons:




    • motor



    • discriminative sensation



    • light touch



  3. Medulla and upper cervical:




    • pain



    • temperature



    • deep touch


REMEMBER:




  • V1: superior orbital fissure



  • V2: foramen rotundum



  • V3: foramen ovale


  1. Medication:




    1. Carbamazepine: progressive increase to maximum dose of 400 mg TID


      CAUTION: monitor levels + complete blood count



    2. Gabapentin: progressive increase to maximum 1,200 mg TID



    3. Baclofen: progressive increase to 20 mg QID



    4. Phenytoin: IV in crisis or oral CAUTION: monitor levels + blood tests



  2. Surgical procedure: Consider when medications are no longer effective OR significant medication side effects occur:




    1. Percutaneous procedures




      1. Balloon compression



      2. Glycerol injection



      3. Radiofrequency (RF) rhizotomy


      FOR ALL PERCUTANEOUS PROCEDURES:


      Performed with monitored anesthesia care (MAC; i.e., propofol + fentanyl or similar) and local anesthesia injected at entry point


      Indications:




      • Elderly patients



      • Contraindication to craniotomy



      • Immediate pain relief required


      Technique:




      • C-arm guidance: true lateral fluoroscopy (acoustic meatus from both sides MUST align)



      • Coordinates:




        1. ENTRY POINT: Mark point 3 cm lateral to the angle of mouth



        2. Mark point 3 cm anterior to tragus



        3. Mark point at medial ipsilateral pupil




      • Insert needle at ENTRY POINT



      • Advance needle toward TARGET POINT (foramen ovale) at intersection of petrous bone with clivus line on lateral X-ray




      • When needle passes into foramen ovale:




        • wincing, tear drops, and masseter contraction are often observed



        • change in resistance of needle is noted (cartilage)



        • Possible CSF return



      • Balloon compression:




        • Attach external pacemaker (risk of bradycardia)



        • Patient in supine position



        • C-arm guidance



        • Place needle (14 gauge) into foramen ovale and advance balloon through the needle



        • Always place blocking device to avoid movement of balloon during inflation



        • Fill balloon with contrast dye and confirm position on lateral X-ray (pear shape appearance of balloon)



        • Inflate balloon at 1.5 atmospheric pressure for 60–90 s



        • Watch for bradycardia (consider atropine before inflation)



        • Balloon may rupture (not dangerous)



      • Glycerol injection:




        • Performed with patient in sitting position, head slightly flexed



        • Place 25-gauge spinal needle not beyond clival line on lateral X-ray



        • Inject up to 0.5-mL dye into trigeminal cistern until the dye starts to “run off” toward posterior fossa and note injected amount



        • Inject equal amount of 99.9% anhydrous glycerol + tantalum powder



      • RF rhizotomy:




        • Patient in supine position



        • Place RF needle with 5 mm exposed tip into foramen ovale to target location



        • Perform MANDATORY electrical stimulation:




          1. SENSORY HIGH frequency (50 Hz) 0.1–0.2 V (max 0.5 V) reproduces pain with facial flushing in corresponding trigeminal branch



          2. MOTOR LOW frequency (2 Hz) MUST produce visible masseter contraction (from motor fibers of V3)


      Producing RF lesion:




      • 70°C



      • 70 s



      • For redo procedures and high voltage (0.5 V) on sensory stimulation: choose 80°C for 80 s


      CAUTION:




      • i. Needle tip in RF rhizotomy MUST NEVER be >5 mm beyond clival line



      • ii. DO NOT PROCEED with RF lesioning if electrical stimulation results are not clear




        • No masseter contraction: electrode not in foramen ovale



        • Eye deviation: the electrode is too deep (CN III, IV, or VI)



        • Face grimacing: the electrode is in posterior fossa (CN VII)



        • Visual disturbance: electrode is touching optic nerve (superior orbital fissure)


      Complications of ALL percutaneous procedures:




      • Numbness (extremely common)



      • Loss of corneal reflex, keratitis (rare)



      • Anesthesia dolorosa (very rare)



      • Masseter weakness



      • Arterial bleeding (Tx: retropharyngeal compression + ICU + delayed angiogram)



      • Meningitis (including aseptic meningitis)


      REMEMBER:




      • V1: difficult with RF



      • Glycerol: highest recurrence rate



      • Balloon: lowest corneal numbness rate



      • Percutaneous procedures can be repeated multiple times



    2. Microvascular decompression


      Indications:




      • Expected survival is more than 5 y



      • Age < 65 y



      • V1 distribution


      Technique:




      • Park-bench position




        • Painful side up



        • Head flexed



        • Head turned 15 degrees to the floor



        • No lateral tilt



      • Consider neuromonitoring (BAEP)



      • Retrosigmoid craniotomy



      • Retract superolateral cerebellum to inferior-medial direction with small blade



      • Open subarachnoid space at petrosal vein and release CSF



      • Identify trigeminal nerve root entry zone: usually much more superior than expected



      • Dissect arachnoid around nerve root and place small Teflon piece between nerve and compressing vessel


      Complications:




      • Hearing loss (VIII)



      • facial dysesthesia (V)



      • facial weakness (VII)



      • craniotomy complications


      REMEMBER:




      • The Most effective procedure for trigeminal neuralgia



      • Not indicated for MS patients (percutaneous rhizotomy preferred).



    3. Stereotactic radiosurgery of nerve root entry zone


      Indications:




      • Elderly patients who don’t require immediate pain relief



      • Patients on anticoagulation



      • Recurrent pain after previous procedure



      • Patient preference


      Technique:




      • Single isocenter 70–90 Gy treatment dose



      • Procedure can be repeated ONCE (with cumulative radiation dose of 140 Gy)


      Complications:




      • Facial hypesthesia in 20% (30% with retreatment)



      • NO severe morbidity



      • NO mortality


      Comments:




      • Well tolerated



      • Does not offer immediate relief (latency 1–3 mo)


Rate of success of all procedures:


I: immediate


M: medium term 1–5 y


L: long term >5 y


BC: balloon compression


GL: glycerol


RF: radiofrequency


MV: microvascular decompression


SR: stereotactic radiosurgery


Glossopharyngeal neuralgia




  • Paroxysmal unilateral stabbing pain in:




    • tonsils



    • base of tongue



    • external auditory meatus



    • angle of mandible



  • Possibly hypotension



  • Syncopal episodes



  • Triggers:




    • talking



    • chewing



    • swallowing



    • coughing



  • No neurological deficit

MRI and MRA brain


Application of 10% cocaine on pharynx reduces pain significantly (may help in differential diagnosis)


  1. Medication: low response rate




    • Antiepileptics (topiramate)



    • Antidepressants



  2. Surgery:




    1. Microvascular decompression:




      • Follow sigmoid sinus to the jugular foramen where CN X and XI separate from CN IX



      • Vessel compression typically from posteroinferior cerebellar artery (PICA)



    2. Rhizotomy:




      • It is usually safe to section all of CN IX and upper 1/6 of CN X



      • avoid in case of contralateral pathology of CN X or gag dysfunction


    Complications:




    • Permanent dysphagia



    • Vocal cord paralysis



    • Intraoperative and immediate postoperative cardiac complications



  3. Stereotactic radiosurgery




    • CN IX is targeted at glossopharyngeal meatus of jugular foramen



    • 80- to 90-Gy single isocenter


Geniculate neuralgia AKA Hunt’s neuralgia AKA Neuralgia of the nervus intermedius (nerve of Wrisberg)




  • Very intense pain deep inside the ear on one side that may be accompanied by burning sensation in part of ipsilateral face



  • Pain may coexist with:




    • bitter taste



    • salivation



    • tinnitus



    • Vertigo


  • Exclude herpes infection



  • MRI/MRA brain



  • ENT evaluation

Hemifacial spasm may coexist (convulsive tic)


  1. Medication:




    1. Antiepileptics



  2. Surgery:




    1. Microvascular decompression (cutting the nervus intermedius)



    2. Section of geniculate ganglion


Postherpetic neuralgia




  • Most common: thoracic roots (2/3 of cases)



  • Second most common: V1 distribution (20% of cases)



  • Continuous causalgia often leads to allodynia (even the light touch of clothes is perceived as painful)


  • Diagnosis is based on history and clinical findings



  • REMEMBER: zoster ‘sine herpete’ is just like normal herpes zoster BUT without vesicles

Varicella zoster AKA herpes zoster AKA human herpes virus type 3 lies dormant in cranial nerves, dorsal and autonomic ganglia until reactivation


  1. Antiherpetic medication (acyclovir, famciclovir, valacyclovir)




    • Reduce the risk of postherpetic neuralgia (especially if given in first 72 h)



    • Corticosteroids given acutely during zoster infection are ineffective in preventing postherpetic neuralgia



  2. Pain medication:




    • Antiepileptics (especially gabapentin)



    • Tricyclic antidepressants



    • Opioids: oxycodone (preferred); tramadol



    • Lidocaine patch



    • Capsaicin (patch or cream)



  3. Pain management procedures (for drug resistant cases):




    1. Intrathecal methylprednisolone + lidocaine: effective long term (but not studied for V1 postherpetic neuralgia)



    2. Nerve blocks (only temporary relief)



    3. Dorsal column stimulation > intrathecal pump > DREZ (Dorsal Root Entry Zone) lesion






  1. Nucleus caudalis DREZ lesion:




    • Suboccipital craniotomy



    • Lesion in the trigeminal nucleus that extends from C2 DREZ to obex (2 mm dorsal to CN XI exit)



    • Distance between C2 DREZ and obex is ~2 cm



    • Entry of DREZ lesioning probe is at 45 degrees



    • Lesions every 1 mm for 15 sec at 80°C



    • DREZ electrode length is 1.2–2.0 mm


    Prognosis: 70% of patients have significant improvement


    Complications:




    • A\taxia (spinocerebellar tract)



    • Weakness (pyramidal tract)


Other facial pain conditions


Trigeminal neuropathic pain




  • Burning constant pain



  • Numbness is common

MRI

After accidental trauma to trigeminal nerve system

Motor cortex stimulation


Trigeminal deafferentation pain (including anesthesia dolorosa)


Very similar to trigeminal neuropathic pain

Diagnosis based on history

After intentional trauma to trigeminal system (i.e., previous rhizotomies, DREZ lesions)

Motor cortex stimulation


Atypical facial pain


Constant or paroxysmal with long duration

MRI (to rule out tumors, MS, etc.)

Term often used for facial pain that does not fit other categories


  • Often psychogenic



  • DO NOT offer surgical treatment options

Note: Medications to be considered in facial neuralgias: carbamazepine, gabapentin, valproic acid, pregabalin, topiramate, phenytoin, amitriptyline, duloxetine.



7.1.2 Motor Cortex Stimulation (Table 7.1b)w


















Indications

Other

Surgical technique



  • Neuropathic pain of face and limbs



  • Best indication is:




    1. neuropathic facial pain (pain after injury to CN V) OR



    2. trigeminal deafferentation pain (facial pain resulting from surgery to treat trigeminal neuralgia)



  • Central pain from thalamic, putaminal, lateral medullary stroke



  • Less experience in:




    1. Phantom limb pain



    2. Spinal cord injury pain



    3. Postherpetic neuralgia


  • Stimulation increases cerebral blood flow in:




    1. Ipsilateral thalamus



    2. Cingulate gyrus



    3. Brainstem



  • Stimulation is not perceived as paresthesia



  • There is no reliable way to predict response



  • Generally expected response:




    • 50% pain relief



    • 50% of patients


  1. Total intravenous general anesthesia (TIVA) like awake craniotomy



  2. Target is the primary motor cortex corresponding to pain area (i.e., face area of motor cortex for facial pain, etc.)



  3. Craniotomy over central sulcus



  4. Electrodes are placed epidurally PERPENDICULAR to central sulcus spanning motor and somatosensory cortex (subdural placement has been described)



  5. Median nerve somatosensory evoked potentials (SSEPs) are recorded while moving the electrode from cranially to caudally until identification of hand region is achieved



  6. Identify the region of phase reversal by moving paddle electrode (phase reversal means one electrode is on motor cortex and one is on somatosensory cortex)



  7. Identify the threshold for contralateral motor response (200-μs pulse width, up to 20 mA). CAUTION: be prepared for seizures



  8. Final four-plate electrode is placed over identified area of motor cortex (PARALLEL to central sulcus).



  9. Electrode is sutured to the dura.



  10. Repeated programming of electrode is performed in postoperative phase



  11. Postoperative stimulation parameters:




    • Voltage: 2–5 V



    • Pulse width: 50–450 μs



    • Frequency: 50 Hz



  12. Activate in the first 24 h from surgery, but it may take weeks to have results



  13. Some contacts may not be activated



  14. Settings are progressively adjusted



  15. Goal: maximal pain relief without seizures


Complications:




  • Seizures (usually during titration programming) → iced saline should be available intraoperatively



  • Infection



  • Failure to relieve pain



  • Hemorrhage



  • Device malfunction



7.1.3 Dorsal Root Entry Zone Lesioning Procedure (Table 7.1c)













































Indications: deafferentation pain

Target

Results

Treatment

Postherpetic facial neuralgia


Nucleus caudalis of CN V

Excellent

Administer intraoperatively iv 1–2 mg/kg/h methylprednisolone throughout the procedure


Depending on level:




  1. Cervical




    • Laminectomy: start one level above level of pain



    • Entry into spinal cord: at highest dermatomal level of pain



    • Inter-root distance: close



    • Rootlets: 5–8



  2. Thoracic




    • Laminectomy: start at least two levels above highest level of pain



    • Entry into cord: two levels above highest dermatome of pain



    • Inter-root distance: far (5 mm between)



    • Rootlets: 2–4



  3. Lumbar/sacral




    • Laminectomy: start at conus



    • Entry into cord: conus



    • Inter-root distance: very close



    • Nerve roots at higher levels are more dorsal and hide the lower ones


Surgical technique:




  • The DREZ is located at the intermediolateral sulcus (i.e., the sulcus lateral to the dorsal columns where sensory rootlets enter into spinal cord) and involves REXED laminae 1–4



  • Lesioning performed caudal to rostral so as to identify upper most root of interest



  • Lesions every 1 mm (more lesions are associated with better results)



  • Enter at 45-degrees angle (similar to root)



  • Depth of 2 mm for spinal cord and 1.2 mm for nucleus caudalis DREZ



  • Duration of 15 s at 75°C



  • El-Naggar–Nashold DREZ electrode (Cosman Medical Inc, Burlington, MA)



  • Mobilize serpentine vessels so that they do not attach to electrode



  • Tack up stiches to dura to avoid epidural hematoma



  • Consider postoperative steroids


Main complications:




  • CSF leakage



  • Epidural hematoma



  • Ipsilateral weakness (corticospinal tract): permanent in 5% of patients



  • Walking difficulty, ataxia


Prognosis:




  • 75% of patients have a good response



  • Response rate decreases over time


Cervical avulsion (brachial plexus) injury


Cervical

Localization:




  • Find the unaffected root on top and the unaffected root on bottom



  • Draw an imaginary line and compare to contralateral side

Excellent


Postherpetic thoracic neuralgia


Thoracic

Use SSEPs and electrodes on spinal cord to identify the largest amplitude

Mediocre


Paraplegia pain (postspinal cord injury)




  • Top of DREZ lesion should be at level of first unaffected root



  • Drain syrinx (shunt)

Good


Phantom limb pain


Conus


Good


Conus avulsion injury


Localization for lumbosacral avulsion: depends on exact level, but remember that avulsed level may be hidden by other more superior roots that have to be moved laterally to directly identify the affected root

Good



7.1.4 Sympathectomy (Table 7.1d)












































Indications

Presentation

Diagnostics

Treatment and others

Surgical technique

Raynaud’s disease




  • Digital arterial vasospasm triggered by cold or stress



  • Extremities (fingers and toes) feel cold, numb, progressively change color from white to blue to red

Exclude secondary form:




  • Connective tissue disorders (in 50%)



  • Medications



  • Smoking


  • Vasoconstriction is caused by sympathetic input



  • Vasodilation caused by dysfunction of mast cells (releasing histamine)



  • Histamine release probably more responsible for disease


  1. Thoracic (upper extremities sympathectomy):




    1. Supraclavicular



    2. Posterior paravertebral costotransversectomy



    3. Axillary transthoracic



    4. Video-assisted thoracoscopic surgery (VATS)



    5. CT-guided chemical sympathectomy


    REMEMBER: the sympathetic chain runs parallel to spine, each ganglion being a swelling within the chain, right under the rib head


    Target: sympathetic ganglia T2, T3, and T4 + accessory nerve of Kuntz (arises from ramus communicans of T2, conducts sympathetic signals)




    • Never remove T1 stellate ganglion because of risk of Horner’s syndrome



    • Remove T2, T3,–T4



    • Monitor palmar skin temperature (unilateral increase of 1–3°C in 10–20 min predicts good results)



    • Sympathectomy T2, T3, T4, and T4 may also offer benefit in plantar hyperhidrosis



  2. Lumbar (lower extremities sympathectomy)




    • Retroperitoneal extreme lateral approach



    • Remove L2–L3 sympathetic ganglion



    • Lateral aspect of vertebral body:




      1. Right side: vena cava



      2. Left side: aorta (right side is more difficult)


Complex regional pain syndrome OR reflex sympathetic dystrophy syndrome


See Table 7.1e


Hyperhidrosis




  1. Primary: focal (palm, feet, face, axilla)



  2. Secondary (generalized)




    • Sweating of palms is most prominent sign



    • Incidence: 1%

Consider:




  • Hodgkin’s lymphoma



  • Hyperthyroidism



  • Tumor of hypothalamus



  • Diabetes



  • Acromegaly



  • Parkinsonism



  • Pheochromocytoma


  • Sweating is sympathetically mediated



  • Neurotransmitter is acetylcholine



  • Nonsurgical treatment options:




    1. Oral anticholinergic (glycopyrrolate, oxybutynin)



    2. Iontophoresis



    3. Botox injections (for underarms and hands)


Compensatory hyperhidrosis syndrome (increased sweating in nonaddressed areas) often occurs after sympathectomy and usually improves in 6 mo


Pancreatic carcinoma





Thoracic sympathectomy: T5–T11


Intractable angina




Rare indication



7.1.5 Treatment Strategies for Various Pain Conditions (Table 7.1e)
















































Disease

Presentation

Diagnostics

Other

Treatment

Dejerine–Roussy (thalamic pain syndrome)


Contralateral hypesthesia and paresthesia may progress in weeks or months to burning sensation, dysesthesia and allodynia

MRI brain: thalamic stroke




  1. Medications:




    • Anticonvulsants (pregabalin, gabapentin)



    • Antidepressants (tricyclics and selective serotonin reuptake inhibitors [SSRIs])



  2. Surgery (from most to least effective):




    1. Motor cortex stimulation



    2. Deep brain stimulation



    3. Dorsal column stimulation


Complex regional pain syndrome (reflex sympathetic dystrophy syndrome)




  • Causalgia, allodynia



  • Autonomic nervous dysfunction (sweating, edema)



  • Trophic changes (skin, hair, nails)



  • Reduced range of motion and weakness

No specific high-sensitivity diagnostic tests known


  1. Type I: without nerve injury



  2. Type II: after nerve injury (median, ulnar and sciatic nerves are most commonly affected)


  1. Physical therapy



  2. Transcutaneous electrical nerve stimulation (TENS)



  3. Acupuncture



  4. Medications




    1. Carbamazepine



    2. Tricyclic antidepressants



  5. Surgical options




    1. Sympathectomy (T2–T4 for arm and L2–L3 for leg)—see Table 7.1d



    2. Sympathetic block: (use fluoroscopy or CT)




      • i. Stellate ganglion (for upper extremity):




        • 22-gauge needle



        • Patient is supine with head tilted backward



        • Target: anterior tubercle of C6



        • Withdraw 1–2 mm (and aspirate to avoid intravascular injection):



        • 20-mL lidocaine 1%



        • If the block is successful, Horner’s syndrome will present



        • NEVER perform bilateral block (risk of laryngeal paralysis)



      • ii. Lumbar (for lower extremity):




        • Patient prone



        • 22-gauge spinal needle



        • Target: 4 cm deeper and cephalad to transverse process of L2–L3–L4



        • 8-mL lidocaine 1% per level (aspirate before injection)



        • CAUTION: transient orthostatic hypotension—bed rest for several hours



    3. Dorsal column stimulation (electrodes ipsilateral to side of pain)



    4. Intrathecal medication pump


Cancer pain in terminally ill patients


Pain below clavicle (C4/C5) that does not respond to medication in patient with life expectancy usually <12 mo

Diminishing response to strong opioids


  • 10% of cancer patients will require interventional techniques for pain management



  • Excellent results in malignant pleural mesothelioma

Percutaneous cervical chordotomy (anterolateral):




  • NEVER bilateral (risk of central hypoventilation syndrome = Ondine’s curse with no spontaneous breathing)



  • ALWAYS perform contralateral to pain



  • Performed at C2 level with CT (or fluoroscopic) guidance and patient supine


Target:




  1. In lateral projection: midpoint between posterior limit of body of C2 and anterior of C2 spinous process (remaining on top level of lamina to avoid the exiting nerve)



  2. In anteroposterior (AP) projection: there is dura penetration when the needle is at the level of odontoid


Goal: interruption of anterolateral spinothalamic tract:




  1. Cervical fibers anterior



  2. Sacral fibers posterior


Dentate ligament:




  • First inject contrast to identify dentate ligament (= posterior limit of spinothalamic tract)



  • CAUTION: ALWAYS stay ANTERIOR to dentate ligament


Electrophysiology:




  • Impedance increases upon entering spinal cord tissue



  • Motor stimulation at 2 Hz, 1–3 V should not cause any contralateral arm or leg contractions



  • Sensory stimulation at 100 Hz, <1 V SHOULD cause paresthesias in contralateral arm or leg



  • Muscle tetany indicates closeness to corticospinal tract (electrode is TOO POSTERIOR)



  • Lesion: 70°C for 30 s




    • Check on movement responses



    • Depth of RF lesion should be <5 mm (avoid lesion to reticulospinal tract to prevent respiratory complications)



    • Ipsilateral Horner’s is to be expected with successful lesion


Success rate:




  • 90% immediate relief



  • 60% at 1 y



  • 40% at 2 y


Complications: ataxia, weakness, bladder dysfunction


Bilateral visceral pain below thoracic level


Patients with cancer pain of the abdomen, pelvis or lower extremities that do not respond to medication



Commissural myelotomy:


Medial longitudinal spinal cord incision to interrupt pain fibers crossing in anterior commissure


Prognosis:




  • 60% complete relief



  • 30% partial relief



  • 10% have no relief



  • Effect usually lasts <1 y


Complications:




  • Bladder dysfunction



  • Sexual dysfunction



  • Weakness



  • Dysesthesias


Cancer pain from breast and prostate cancer


Terminally ill cancer patients with agonizing pain





  • Surgical or radiosurgical hypophysectomy



  • Effectiveness reported also in tumors without hormone dependence



  • Pain relief in 70%

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May 11, 2020 | Posted by in NEUROSURGERY | Comments Off on 7 Functional Neurosurgery

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