Pontine high-grade glioma

Introduction

Brainstem surgery can be associated with significant morbidity and mortality. ^, This high risk of neurologic injury is owing to the fact that the brainstem has a high density of eloquent gray and white matter structures, including cranial nerve nuclei, cranial nerve tracts, and craniospinal tracts, among others. ^, With improvements in neuroimaging, advances in surgical techniques, and improved mapping paradigms, surgery within the brainstem can occur with reduced morbidity. ^, In this chapter, we present a case of a likely high-grade lesion within the pons.

Example case

Chief complaint: double vision

History of present illness

A 46-year-old, right-handed man with no significant past medical history presented with double vision. Over the past 4 to 5 months, he has complained of progressive double vision to the point where he cannot drive. Imaging was done and revealed a brain lesion ( Fig. 30.1 ).

Medications : None.
Allergies : No known drug allergies.
Past medical and surgical history : None.
Family history : No history of intracranial malignancies.
Social history : Farmer. No smoking or alcohol.
Physical examination : Awake, alert, oriented to person, place, and time; Language : intact naming and repetition; Cranial nerves II to XII intact except right eye abduction weakness and dysconjugate gaze; No drift, moves all extremities with full strength; Cerebellar: no finger-to-nose dysmetria.

	Bob S. Carter, MD, PhD, Massachusetts General Hospital, Boston, MA, United States	Shlomi Constantini, MD, Danil A. Kozyrev, MD, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel	Alessandro Olivi, MD, Giuseppe Maria Della Pepa, MD, Fondazione Policlinico Universitario Agostino Gemelli IRCSS, Catholic University of Rome, Rome, Italy	Andrew E. Sloan, MD, University Hospital, Case Western Reserve Cleveland, OH, United States
Preoperative
Additional tests requested	CSF analysis	MRI diffusion Spine MRI PET	DTI MRS	CT chest, abdomen, pelvis CSF analysis Hearing test Serum ACE levels DTI
Surgical approach selected	Right suboccipital stereotactic needle biopsy	No surgery, radiation therapy only	Right suboccipital retrosigmoid craniotomy for excisional biopsy with 5-ALA	Right suboccipital retrosigmoid craniotomy for excisional biopsy
Anatomic corridor	Right middle cerebellar peduncle		Lateral perimedullary cistern	Lateral perimedullary cistern
Goal of surgery	Diagnosis		Diagnosis	Diagnosis
Perioperative
Positioning	Right supine		Right park bench	Right supine with 90 degree left rotation
Surgical equipment	Surgical navigation Biopsy kit		Surgical navigation IOM (MEP/SSEP), nerve stimulator Surgical microscope with 5-ALA Ultrasound	Surgical navigation IOM (MEP, EMG cranial nerves 7/8, BAERs) Surgical microscope
Medications	None		Steroids Possible mannitol	Steroids Mannitol Antiepileptics
Anatomic considerations	Pons, medulla		Vertebral artery, PICA, lower cranial nerves, transverse-sigmoid sinuses, jugular bulb	PICA, AICA, brainstem nuclei, cranial nerves 7/8
Complications feared with approach chosen	Corticospinal tract injury, cranial neuropathy	High risk of neurologic injury with surgical approaches	Vascular injury, CSF leak, cerebellar retraction injury	Brainstem manipulation
Intraoperative
Anesthesia	General		General	General
Skin incision	Linear		Right paramedian linear	Right retrosigmoid
Bone opening	Right suboccipital burr hole		Suboccipital below transverse sinus and medial to sigmoid sinus	Suboccipital below transverse sinus and medial to sigmoid sinus
Brain exposure	Right cerebellar hemisphere		Lower suboccipital to expose lateral perimedullary cistern	Lower suboccipital to expose lateral perimedullary cistern
Method of resection	Linear incision 3–4 cm based on surgical navigation, burr hole based on navigation, open dura, single core biopsy targeting wispy enhancing area above main area of enhancement, review personally with pathology, avoid second pass if possible		Use cranial landmarks to identify transverse-sigmoid junction to plan incision, craniotomy based inferior to this centered over the enhancing region at the lower lateral perimedullary cistern, anterior-based dural flap to enter cerebellopontine cistern, confirm trajectory with navigation, stimulate lateral brainstem to find safe entry zone, sample both contrast-enhancing and nonenhancing areas aided with 5-ALA, watertight dural closure with pericranium if needed, inspection and waxing of mastoid air cells	Use navigation and cranial landmarks to identify transverse-sigmoid junction based on position of zygoma and asterion, craniotomy below the transverse-sigmoid junction, curvilinear dural opening, location of tumor confirmed with navigation, expose lateral perimedullary cistern, find transsulcal approach based on DTI to enter tumor and sample, stop resection once diagnosis confirmed
Complication avoidance	Needle biopsy, one core specimen		Brainstem mapping, 5-ALA, excisional biopsy	DTI, transsulcal entry, stop after diagnosis obtained
Postoperative
Admission	ICU		ICU	ICU
Postoperative complications feared	Worsening double vision		Respiratory failure, dysphagia, tongue weakness, vocal cord dysfunction	Injury to cranial nerves 7 and 8, CSF leak, retraction injury
Follow-up testing	CT immediately after surgery		Swallow evaluation	MRI within 48 hours after surgery
Follow-up visits	7–10 days after surgery		10 days after surgery MRI 3 months after surgery	10–14 days after surgery
Adjuvant therapies recommended
Diffuse astrocytoma (IDH mutant, retain 1p19q)	STR–radiation/temozolomide GTR–radiation/temozolomide	STR–radiation GTR–not possible	STR–temozolomide +/– radiation GTR–temozolomide +/– radiation	STR–radiation/temozolomide or PCV GTR–radiation/temozolomide or PCV
Oligodendroglioma (IDH mutant, 1p19q LOH)	STR–radiation/PCV GTR–radiation/PCV	STR–radiation GTR–not possible	STR–temozolomide GTR–temozolomide	STR–radiation/temozolomide GTR–radiation/temozolomide
Anaplastic astrocytoma (IDH wild type)	STR–radiation/temozolomide GTR–radiation/temozolomide	STR–radiation GTR–not possible	STR–radiation/temozolomide GTR–radiation/temozolomide	STR–radiation/temozolomide GTR–radiation/temozolomide