Parietal low-grade glioma

Introduction

The parietal lobe is often considered a safe entry point for cortical and subcortical tumors because it avoids the somatosensory cortex anteriorly and the visual cortex posteriorly. However, there are a variety of parietal lobe symptoms that can develop from accessing lesions in this region, which include Gerstmann syndrome (right-left confusion, agraphia, and acalculia), aphasia, and agnosia in the dominant hemisphere, as well as constructional apraxia, dressing apraxia, and anosognosia in the nondominant hemisphere. In a study on parietal lobe gliomas, 34 of 119 (29%) parietal gliomas were low-grade gliomas (LGGs). The most common deficits following parietal glioma surgery were dysphagia, sensory deficits, vision changes, and parietal lobe syndromes that occurred in 26% of patients. In this chapter, we present a case of a nondominant-hemisphere, parieto-occipital, LGG.

Example case

Chief complaint: headaches

History of present illness

A 46-year-old, right-handed woman with hypertension presented with headaches. She has had intermittent episodes of excruciating headaches without nausea or vomiting that were different from her typical headaches. She was seen by her primary care physician who ordered imaging, which revealed a brain lesion ( Fig. 9.1 ). She was referred for evaluation and management.

Medications : Lisinopril.
Allergies : No known drug allergies.
Past medical and surgical history : Hypertension.
Family history : No history of intracranial malignancies.
Social history: Cashier. No smoking, occasional alcohol.
Physical examination : Awake, alert, oriented to person, place, and time; Language: intact naming and repetition; Cranial nerves II to XII intact; No drift, moves all extremities with full strength.

	Hugues Duffau, MD, PhD, University Hospital of Montpellier, Montpellier, France	Shawn L. Hervey-Jumper, MD, University of California at San Francisco, San Francisco, CA, United States	Randy L. Jensen, MD, PhD, University of Utah, Salt Lake City, UT, United States	Stephen J. Price, MBBS, PhD, University of Cambridge, Cambridge, United Kingdom
Preoperative
Additional tests requested	Neuropsychological assessment Repeat MRI for growth rate fMRI+DTI (research)	DTI MEG Neuropsychological assessment	Ophthalmology (visual field testing)	Ophthalmology (visual field testing) MRI perfusion with rCBV Steroid trial
Surgical approach selected	Right parietal awake craniotomy with cortical and subcortical mapping of precuneus, posterior cingulate, and splenium	Right parieto-occipital craniotomy with cortical and subcortical mapping	Right occipital craniotomy with interhemispheric	Right occipital craniotomy with 5-ALA if no response to steroids and rCBV greater than 3
Anatomic corridor	Right superior parietal lobule	Right parieto-occipital cortex	Right occipital interhemispheric	Right occipital interhemispheric
Goal of surgery	Extensive resection (GTR or NTR) with preservation of neurologic and cognitive functions	GTR with patient agreeing to accepting hemianopsia	GTR with expected visual field deficits	Resection of tumor with likely hemianopia
Perioperative
Positioning	Lateral	Prone	Prone	Prone
Surgical equipment	Brain stimulator Dedicated team (anesthesia, neuropsychological, speech pathology) No neuronavigation, intraoperative MRI, microscope, or functional neuroimaging	Surgical navigation Surgical microscopeBipolar and monopolar brain stimulator Ultrasonic aspirator	Surgical navigation MEPs Ultrasonic aspirator Intraoperative MRI	Surgical navigation Surgical microscope with 5-ALA Ultrasound Ultrasonic aspirator Budde halo retractor
Medications	Steroids Antiepileptics	Antiepileptics Steroids Mannitol	Steroids	5-ALA Mannitol Steroids
Anatomic considerations	Postcentral sulcus anteriorly, intraparietal sulcus laterally, parieto-occipital sulcus posteriorly; somatosensory thalamocortical pathway anteriorly, SLF II laterally, optic tracts, cingulate	Superior sagittal sinus, callosomarginal and pericallosal arteries, cingulate gyrus	Visual cortex, visual fields	Venous sinuses and draining veins
Complications feared with approach chosen	Sensorimotor deficit, movement control, visual fields, spatial cognition, executive function, mentalizing, conscious awareness	Visual field defects, stroke	Visual field deficit	Hemianopia, central visual defect
Intraoperative
Anesthesia	Asleep-awake-asleep	General	General	General
Skin incision	Arciform mark	U-shaped	Linear	Linear paramedian
Bone opening	Right parietal	Right occipital	Right parietal	Right occipital
Brain exposure	Right central and parietal	Right occipital	Right parietal	Right occipital
Method of resection	Opening under general anesthesia with laryngeal mask airway, bone flap exposing parietal lobe and perirolandic area, patient awoken prior to dural opening after dural anesthesia, cortical mapping at low intensity (1.5–3 mA) with counting/left upper and lower extremities/line bisection task/monitoring visual fields/conscious awareness, subpial dissection concurrent with mapping and functional testing, resection up to functional boundaries of somatosensory tracts/SLF/cingulate/optic tracts, general anesthesia for closure	Right parieto-occipital craniotomy ipsilateral to sagittal sinus, cortical bipolar motor mapping to identify somatosensory cortex, transparietal approach, focus on anterior and medial margins first, subpial dissection down to U-fibers, expose falx/cingulate sulcus/callosomarginal arteries, subcortical monopolar mapping along anterior and lateral margins finish with cingulate resection working medially within cingulate gyrus until corpus callosum is identifiedcortical bipolar motor mapping to identify somatosensory cortex, transparietal approach focus on anterior and medial margins first, subpial dissection down to U fibers, expose falx/cingulate sulcus/callosomarginal arteries, subcortical monopolar mapping along anterior and lateral margins, finish with cingulate resection working medially within cingulate gyrus until corpus callosum is identified.	Right occipital craniotomy, interhemispheric approach, subpial dissection, identify tumor and corticectomy and debulk tumor, continuous MEP monitoring, intraoperative MRI for potential further resection	Right occipital craniotomy with burr holes on midline and spanning contralateral side above transverse sinus, cruciate dural opening and monitor for draining veins, mobilize occipital lobe, CSF drainage, retraction away from visual cortex, mobilize along falx to free end and visualize corpus callosum, blue light with fluorescence (unlikely), ultrasound to visualize best trajectory, continue corticectomy of posterior margin avoiding primary visual cortex, debulk tumor on deeper margin on medial side, rotate right side to get better view of lateral surface and debulk laterally, posterolateral corner may be difficult to visualize, watertight dural closure
Complication avoidance	Cortical and subcortical mapping with counting, left upper and lower extremity movement, line bisection, visual field monitoring, conscious awareness	Subpial resection, cortical and subcortical mapping, cingulate portion last	Interhemispheric approach, continuous MEP recording, intraoperative MRI for further resection	Craniotomy spans to contralateral side, monitor for bridging veins, avoid primary visual cortex, debulk medial side first
Postoperative
Admission	ICU	Intermediate care	ICU	Floor
Postoperative complications feared	Movement, executive functions, spatial cognition, visual field, high-level mentalizing	Stroke, visual field defect (expected)	Visual field deficit	Visual field deficit
Follow-up testing	MRI within 24 hours after surgery Neuropsychological testing 2 days after surgery	MRI within 48 hours after surgeryNeuropsychological testing at 1 and 3 months after surgeryCognitive rehab as needed	MRI within 48 hours after surgery Visual field testing 3 months	MRI within 72 hours after surgery Visual field testing 1 month after surgery
Follow-up visits	Cognitive rehabilitation, MRI 3 months and then every 3–6 months throughout lifetime	14 days after surgery, 1 and 3 months neuropsychological assessments	4–6 weeks after surgery	7 days after surgery
Adjuvant therapies recommended
Diffuse astrocytoma (IDH mutant, retain 1p19q)	STR–observation for growth rate GTR–observation for growth rate	STR–radiation/temozolomide GTR–observation	STR–radiation/temozolomide GTR–radiation/temozolomide	STR–radiation/temozolomide GTR–observation
Oligodendroglioma (IDH mutant, 1p19q LOH)	STR–growth rate observation GTR–growth rate observation	STR–tumor board discussion, likely chemoradiation GTR–observation	STR–radiation/temozolomide GTR–observation	STR–radiation/PCV GTR–observation
Anaplastic astrocytoma (IDH wild type)	Homogenous AA-temozolomide AA foci removal with GTR of FLAIR abnormality–treatment as for diffuse astrocytoma	STR–radiation/temozolomide GTR–radiation/temozolomide	STR–radiation/temozolomide GTR–radiation/temozolomide	STR–radiation/temozolomide GTR–radiation/temozolomide