Medullary brainstem low-grade glioma

Introduction

Brainstem tumors are a rare subset of intrinsic tumors that occur in adults that account for less than 1% of the primary brain tumors in adults. ^, These tumors typically occur in children and younger adults. ^, Surgery for these lesions can be associated with significant morbidity and include significant cranial nerve (CN) dysfunction and motor deficits. ^, Therefore because of the high risk of neurologic deficits, the optimal treatment of intrinsic brainstem lesions remains controversial. ^, In this chapter, we present a case of a medullary brainstem tumor.

Example case

Chief complaint: headaches and progressive imbalance

History of present illness

A 31-year-old, right-handed woman with no significant past medical history presented with headaches, facial pressure, and progressive imbalance. For the past 3 months, she has had progressive sensation of facial pressure and worsened headaches. She was treated with antibiotics for sinusitis, without improvement. More recently, over the past 2 weeks, she has had progressive imbalance with frequent falls. Imaging was done and revealed a brain lesion ( Fig. 14.1 ).

Medications : None.
Allergies : No known drug allergies.
Past medical and surgical history : None.
Family history : No history of intracranial malignancies.
Social history : Accountant. No smoking or alcohol.
Physical examination : Awake, alert, oriented to person, place, and time; CNs II to XII intact; No drift, moves all extremities with full strength; right greater than left finger-to-nose dysmetria.

	Victor Garcia-Navarro, MD, Tec de Monterrey Institute, Campus Guadalajara, Mexico	George I. Jallo, MD, Johns Hopkins All Children’s Hospital, St. Petersburg, FL, United States	Maciej S. Lesniak, MD, Northwestern University, Chicago, IL, United States	Andreas Raabe, MD, University Hospital at Inselspital, Bern, Switzerland
Preoperative
Additional tests requested	MR perfusion Genetic/evaluation evaluation for VHL	Spinal MRI MR angiography	None	DTI Cerebral angiogram
Surgical approach selected	Right far lateral craniotomy	Midline suboccipital craniotomy with cortical and subcortical mapping	Right suboccipital craniectomy	Midline suboccipital craniotomy with cortical and subcortical mapping
Anatomic corridor	Right lateral medullary	Right telovelar	Right lateral medullary	Right telovelar
Goal of surgery	Diagnosis, resect enhancing portion	Extensive resection with cyst decompression and avoiding neurologic deficit	Diagnosis, resect enhancing portion	Diagnosis, resection of enhancing portion and cyst
Perioperative
Positioning	Right park bench	Prone	Right park bench	Prone
Surgical equipment	Surgical navigation IOM (SSEP, MEP, BAERs, cranial nerve 7, 10–12 EMG)	Surgical navigation IOM (SSEP, MEPs, BAERs, cranial nerve EMG) Ultrasound Surgical microscope Nerve stimulator	Surgical navigation IOM Brain stimulator	Surgical navigation Ultrasound IOM (SSEP, MEP, cranial nerve EMG) Brain stimulator
Medications	Steroids Hypertonic saline solution	Steroids	Mannitol Steroids	None
Anatomic considerations	Sigmoid sinus, PCA, cranial nerves 7–12, brainstem, white matter tracts	Cerebellar tonsils, PICA, floor of fourth ventricle	Cranial nerve nuclei and tracts	Cranial nerves 9–12, CST, sensory tracts
Complications feared with approach chosen	Vascular injury, brainstem and cerebellar retraction injury	Lower cranial nerve dysfunction, motor or sensory deficit	Hemiparesis	Lower cranial nerve dysfunction, motor or sensory deficit
Intraoperative
Anesthesia	General	General	General	General
Skin incision	Inverted hockey stick	Midline	Right paramedian	Midline
Bone opening	Extended retrosigmoid suboccipital craniotomy and posterior third of the occipital condyle	Suboccipital craniotomy with foramen magnum and C1 laminectomy	Suboccipital craniectomy	Suboccipital craniotomy with foramen magnum and C1 laminectomy
Brain exposure	Inferior cerebellum, right lateral medulla	Cerebellum and cervicomedullary junction	Inferior cerebellum, right lateral medulla	Cerebellum and cervicomedullary junction
Method of resection	Myocutaneous flap, retrosigmoid suboccipital craniotomy 3–4 cm posterior to sigmoid sinus, skeletonizing of transverse/sigmoid sinus, posterior third of the occipital condyle drilled away, L-shaped dural opening paralleling sinuses, drain CSF from cisterns, identification of neurovascular structures, stimulation to identify safe entry zone, lesion resection at tumor margin with decompression of cyst and removal of enhancing lesion, watertight dural closure with dural substitutes, titanium mesh or bone flap fixation	Midline suboccipital with slight right eccentricity with C1 laminectomy, Y-shaped dural opening, section arachnoid between tonsils, identifying and sectioning tela choroidea +/– inferior medullary velum on right, ultrasound probe and navigation to confirm lesion location if not readily apparent, stimulate with nerve stimulator to confirm no lower cranial nerve activity, intralesional debulking with suction, stop if lesion is fibrous or neuromonitoring changes, watertight dural closure with dural substitute if necessary, bone flap fixation	Right suboccipital craniectomy, identify right lateral medullary area anatomically, stimulate brainstem to find entry point with negative stimulation, resect as much lesion based on continuous monitoring and stimulating of CSTs, watertight dural closure, titanium mesh	Midline suboccipital craniotomy with opening of foramen magnum, +/– C1 laminectomy based on navigation, dural opening, opening of right tela choroidea and inferior medullary velum, expose part of cyst that reaches surface, map dorsal wall using cranial nerve/dorsal column/motor mapping, enter the cyst and spread tissue with fine forceps, release cyst fluid, map again, remove solid enhancing tumor, expected/planned subtotal resection, dural closure, bone fixation
Complication avoidance	Large bony opening, nerve stimulation for safe entry zone, decompress cyst	Opening foramen magnum, right-sided telovelar opening, ultrasound and navigation to confirm lesion, nerve stimulator to identify safe entry zone, intralesional debulking	IOM to guide entry and resection	Motor, dorsal column, and cranial nerve mapping; IOM; resecting only enhancing portion
Postoperative
Admission	ICU	ICU	ICU	ICU
Postoperative complications feared	Hydrocephalus, lower cranial nerve dysfunction	Lower cranial nerve dysfunction, motor or sensory deficit, CSF leak	Hemiparesis, infarct	Lower cranial nerve dysfunction, motor or sensory deficit
Follow-up testing	CT/CTA within 24 hours after surgery ENT evaluation within 24 hours after surgery MRI within 72 hours of surgery	MRI within 48 hours after surgery Swallow evaluation	MRI within 48 hours after surgery	MRI within 48 hours after surgery
Follow-up visits	10–12 days after surgery	14–21 days after surgery	14 days after surgery	4 weeks after surgery
Adjuvant therapies recommended
Diffuse astrocytoma (IDH mutant, retain 1p19q)	STR–radiation/temozolomide GTR–temozolomide	STR–observation GTR–observation	STR–observation GTR–observation	STR–radiation/temozolomide GTR–radiation/temozolomide
Oligodendroglioma (IDH mutant, 1p19q LOH)	STR–radiation/PCV (if available) or temozolomide GTR–observation	STR–observation GTR–observation	STR–chemotherapy GTR–chemotherapy	STR–PCV GTR–not possible
Anaplastic astrocytoma (IDH wild type)	STR–radiation/temozolomide GTR–radiation/temozolomide	STR–radiation/temozolomide GTR–radiation/temozolomide	STR–radiation/temozolomide GTR–radiation/temozolomide	STR–radiation/temozolomide GTR–radiation/temozolomide