Posterior fossa and brainstem tumors in children by Dr. Shikher Shrestha (FCPS), NINAS, Nepal
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Transcript of Posterior fossa and brainstem tumors in children by Dr. Shikher Shrestha (FCPS), NINAS, Nepal
Posterior Fossa and Brainstem Tumors in Children
Shikher ShresthaNINAS
Introduction..
Pediatric brain tumors – leading cause of solid cancer related death in children
~60% of tumors are in infratentorial compartment
Prognosis ranges from excellent to dismal depending on histopathological findings, extent of surgical resection and use of adjunctive therapies
Clinical Presentation
Depends on location and aggressiveness of the lesion
Most common presenting sign – hydrocephalus and symptoms of raised ICP
Focal compression of brainstem – cranial n. deficits and long tract signs
Compression of cerebellum – truncal ataxia and unsteady gait
If leptomeningeal spread – signs and symptoms related to the site of metastasis
Supratentorial spread – seizure and communicating hydrocephalusSpinal spread – symptoms of cord or nerve compression
General Diagnostic imaging features..
MRI both brain and spinal cord to rule out leptomeningeal spread
CSF to look for malignant cells if no contraindication to LP10-14 days should be waited after surgery, if metastatic CSF work up not done preoperatively to rule out false positive result
MRI with DWI and MRS is done to distinguish various tumor subtypes or distinguish relapse from radiation necrosis
Taurine in MRS is seen in medulloblastoma
DWI measures microscopic diffusion of water in tissues. Highly cellular tumors like medulloblastoma have restricted diffusion lower signals on ADC map
Pilocytic Astrocytoma
Most common pediatric cerebellar tumor
Mean age 7-8 yrs
No gender predilection
WHO grade I – slow growth, indolent behavior, high survival rate
Can occur anywhere in the neuraxis, but the cerebellar hemispheres (~50%), optic pathways, thalamus, and hypothalamus are the most common sites
Imaging..
Well circumscribed cystic lesion with a solid enhancing nodule
CT scan:
well demarcated lesion with cyst like featuresvery occasional calcificationintense enhancement of the solid component
with contrast administration
4 imaging patterns found:
enhancing mural nodule or mass with non enhancing cyst
enhancing mural nodule with intensely enhancing cyst
predominantly solid mass with no cyst component
necrotic mass with central non enhancing zone
Typically arise from vermis and cerebellar hemisphere
Can extend into the ventricular system
MRI
hypointense on T1 and hyperintense on T2
may be combined with DWI and MRS to differentiate with less accuracy among medulloblastomas and ependymomas
Leptomeningeal spread is rare but can occur if:
arising from hypothalamus
partially resected
in very young
Histology..
Classic biphasic pattern – loose glial tissue and compact piloid tissue
Loose glial component – protoplasmic astrocytes with eosinophilic granular bodies
Piloid component – dense sheets of bipolar cells with fibrillary process containing Rosenthal fibers
Macroscopically – well circumscribedMicroscopically – 64% show infiltration of the surrounding brain, making surgical extirpation difficult
Degree of mitotic index, cellular atypia and microvascular proliferation has no effect on event free survival
Histopathological evidence of vascular hyalinization, calcification, necrosis or oligodendroglioma-like features may predict a poorer clinical outcome
Very rarely, pilocytic astrocytoma undergo malignant transformation to anaplastic pilocytic astrocytoma usually after radiotherapy
Rarely associated with NF1 unlike supratentorial or brainstem astrocytoma
Genetics – gains at 7q34 resulting in discovery of two important fusion proteins: KIA1546-BRAF and SRGAP3-RAF1 activation of ERK/MAP pathway
Management
GTR – curative
Resection of mural nodule – is the KEY
Debate regarding need of removal of the cystic wall (no statistical difference)
Post op MRI to evaluate the degree of resection
GTR – 10 year survival rates >90%
Spontaneous regression after partial resection has been noted
No adjuvant therapy unless leptomeningeal spread, in which case chemo or radiotherapy given (no standard protocol exists)
Medulloblastoma
Most common malignant solid neoplasm of childhood
Related to PNETs (Primitive Neuro Ectodermal Tumors)
Occurs exclusively in posterior fossa
Median age 9 years in entire population and 7.3 yrs in pediatric population
Slight male predominance 1.6:1
Histology and Genetics
Grade IV WHO lesion
Five subtypes:
classic
desmoplastic/nodular
medulloblastoma with extreme nodularity
anaplastic
large cell
Desmoplastic/nodular – more favorable prognosis than large cell and anaplastic variant
Classic medulloblastoma
small blue cell tumor
densely packed undifferentiated oval cells with hyperchromatic nuclei
marked nuclear pleomorphism and brisk mitotic activity
HOMER WRIGHT ROSETTES – neoplastic cells concentrically arranged around fibrillary processes
Desmoplastic
“pale islands” of reticulin fibers surrounding a nodular reticulin free zone
Large cell/ Anaplastic
large nuclei with prominent nucleoli
lower nuclear/cytoplasmic ratio
Genetics:
Familial syndromes associated in small number of cases Gorlin’s syndrome (mutation in PTCH gene in sonic hedgehog signaling pathway)Turcot’s syndrome (APC gene mutation)Li-Fraumeni syndrome (mutation in p53 tumor
supressor)
Cell of origin – elusive
External granule layer of developing cerebellum or
Subventricular progenitor zone
Recent genetic subgroup analysis classification
Group A – defects in WNT signaling pathwaybehaves like classic
medulloblastoma
Group B – defects in SHH signaling extremes of age (infant or adult)desmoplastic phenotype with more
favorable outcome
Group C – poor prognosis and disseminated disease
Group D – poor prognosis and disseminated disease
N.B> Immunohistochemistry has ability to predict genetic subgroup
Imaging..Typically midline cerebellar lesion arising from vermis
Older children and adults – can arise from cerebellar hemisphere
CT:hyperdense lesion in cerebellar vermissurrounding vasogenic edemacalcification (22%); cyst formation (59%)
MRI:iso/hypointense to white matter in T1 and hyperintense in T2homogenous or heterogenous tumor enhancement14% have foraminal extension33% - leptomeningeal seedingseeding in spinal canal (most common) or supratentorial seedingNodular or diffuse enhancement along the leptomeninges, spinal
nerve roots or cranial nerves in case of CSF seeding
15-60% patients with evidence of mets by MRI have positive CSF cytology
70% patients with positive CSF cytology have evidence of mets in MRI
Rare sites of spread – bone, lymph nodes, liver and lung
Management..
Combined Surgery + Radiation + High dose chemotherapy
5 yr PFS – 80%
Risk stratification – based on age (less than 3 years), presence of disseminated disease and extent of surgical resection
Pitfall – fails to address tumor biology and system based on molecular markers and genetic subgroup analysis
Favorable markers: nuclear betacatenin and TrkC expression
Unfavorable markers: Myc genes and ERBB2
Chang M Staging..
Surgery for Medulloblastoma
Goal – complete resection without causing neurological injuries
Post operative imaging within 24 to 48 hrs
If >1.5 cm2 residual tumor – repeat procedure – if safe and anatomically feasible
Treatment of Children >3yrs with average risk medulloblastoma
Radiosensitive; hence radiotherapy incorporated for age > 3yrs
Dose: 23.4 Gy with posterior fossa boost of 54 Gy, followed by 12 months of chemotherapy
Treatment of Children > 3yrs with High risk medulloblastoma
5 year event free survival – 30-70%
Surgery + craniospinal radiation with 36 to 39.6 Gy
with posterior fossa boost followed by intense
cyclophosphamide, vincristine, cisplatin and peripheral
stem cell rescue
Treatment of Infants and Young Children with medulloblastoma
Developing brain susceptible to the toxicity of treatment regime
Severe neurocognitive decline secondary to craniospinal irradiation
Use of chemotherapeutic strategies to delay or avoid craniospinal radiation until the child reaches 3 years
Overall 5 yrs PFS rate 31.8% but increased to 69% if GTR
Chemotherapy used - cisplatin, vincristine, etoposide and cyclophosphamide
Methotrexate addded for disseminated disease
Salvage strategies
After relapse of medulloblastoma
Myeloablative chemotherapy with autologous stem cell rescue
Intrathecal chemotherapy
Novel therapeutics
Sonic hedgehog (SHH) pathway inhibitor – GDC-0449
Proton Beam therapyutilizes charged beams that have finite range in tissues spares normal tissues compared to conventional
radiotherapyPhase II trial
Intrathecal (IT) chemotherapydelayes radiation therapysalvage recurrent diseasetreat leptomeningeal seedingsuccessfully used to avoid craniospinal radiation in
Pediatric leukemia population
Ependymoma..
Third most frequent brain tumor
1926, Cushing and Bailey 6.4% of primary brain tumors in children (0-14 yrs)30% of tumors in children less than 3 years of age
Mean age of presentation: 3.7 yrs
5 years survival rates: 60%
Can occur throughout the neuraxis
Posterior fossa (fourth ventricle, CPA) more common location (70%)
Imaging
Fills the 4th ventricle
Extends laterally through the foramina of Luschka (15%) and inferiorly through Magendie (60%)
MRI: low T1, high T2 and intermediate to high FLAIR signal intensity
Heterogenous due to calcifications (50%), cystic areas and hemorrhage
Heterogenous enhancement
DWI – intermediate between pilocytic (low) and PNETs (high)
Often encase neurovascular structures in the CPA, making surgical removal difficult
Ikezaki et al. classification
1. Lateral type – presenting in CPA – poor prognosis secondary to involvement of cranial nerves and brainstem
2. Localized to 4th ventricle floor – intermediate prognosis3. Localized to roof of 4th ventricle – most favorable outcome
Leptomeningeal spread – 8-12% - more frequently with anaplastic grades
Leptomeningeal disease with drop metastasis – most common in lumbosacral region
Histology..
WHO – three grades and 4 histological variants
Classical histological features:
Perivascular and ependymal rosettesPerivascular : Ependymal cell processes radially
arranged around a cell-free perivascular zoneEpendymal: tumor cells concentrically arranged to
form lumen
Anaplastic:
1. brisk mitotic activity2. Increased cellularity3. Microvascular proliferation4. Pseudopallisading necrosis
Genetics:
most common genetic alteration is loss of chromosome 22
other genetic events: 9q and 1q gain, loss of 6q, and monosomy 17p
DNA identical to portions of SV40 virus isolated (SV40 – capable of inducing ependymoma in rodents)
Surgical Management..
Key: complete macroscopic surgical resection
Degree of resection is the most significant predictor of survival
Goal of surgery: tissue diagnosis, management of hydrocephalus and cytoreduction
5 years survival after complete surgical resection: 70-80%
If subtotal resection: 5 yr survival – 20-40%
“Second look” surgery if bulky residual tumor after initial surgery
Morbidity of complete resection when CPA extension and 4th ventricular floor involvement is high (10-30%)
Adjunctive therapy..
Radiosensitive tumor hence postoperative radiotherapy
7 yrs EFS and OS of 69% and 81% with maximal surgical resection and local conformational radiation therapy (St. Jude Children’s Research Hospital)
Craniospinal irradiation – only if CSF dissemination by imaging or cytology
Moderate success of chemotherapy, which is used to delay radiation in young children
Current study: molecularly targeted therapy – small molecule tyrosine kinase inhibitors (geftinib, erlotinib, bevacizumab)
Relapse rate: 30-72%
Majority of relapse occurs locally
Median survival time after relapse – 8.4 to 24 months
Literature supports reoperation for recurrence or radiation in children who have not received radiotherapy
Reradiation in children with previous radiation will have high morbidity from radiation necrosis
Atypical Teratoid/Rhabdoid Tumor
Malignant Rhabdoid Tumor – first described as a highly malignant subtype of Wilm’s Tumor
Biggs et al – first intracranial MRT in 1987
Named as atypical teratoid/rhabdoid tumor in landmark paper 1995
Histological character – neuroepithelial, peripheral epithelial and mesenchymal elements
WHO recognized it as a separate tumor entity in 2000
Predominantly a tumor of infants and young children
Median age – 26 months
Slight male predominance
30% - occur infratentorially (CPA and cerebellum)
22% has CSF dissemination at the time of diagnosis
Overall survival 18 months
If signs of metastasis – 8 months
Histology:
nests or sheets of rhabdoid cells intermixed with areas indistinguishable from PNET or medulloblastoma
histopathological diagnosis aided by staining for the loss of nuclear INI 1 (tumor supressor gene found on chromosome 22q)
60-90% - monosomy or deletions of chromosome 22
Imaging:
no distinguishing features from other fourth ventricular tumor
Management:
GTR correlated with OS and PFS
Radiation therapy – craniospinal or focal – important in control
high dose alkylator chemotherapy used with significant benefit in EFS
cisplatin, stem cell rescue and intrathecal chemotherapy
still remains a therapeutic challenge
Choroid Plexus Papilloma and Carcinoma
Rare primary brain tumors arising from choroid plexus epithelium
Guerard described first in 1833
Bielschowsky performed first operative procedure in 1906
0.4 -0.8% of all primary brain neoplasms
70% diagnosed before the age of 2 yrs
Slight male predominance 1-1.3:1
WHO grades
I – choroid plexus papilloma
II – atypical CPP
III – choroid plexus carcinoma
Anatomically, occurs more frequent in lateral (50-70%), fourth (20-40%) and third (5-10%) ventricles
CPA and biventricular location (5%)
Younger children – lateral ventricle vs. older children 4th vent and CPA
Metastasis – anywhere in neuraxis
Histology and Genetics:
Li-Fraumeni, NF2, Aicardi’s, Down, von-Hipple Lindau – associated
Germline mutation in TP53 and hSNF5/INI1 – familial cases
Gain of 9p and loss of 10q – survival advantage
Histologically similar to normal choroid plexus
Many papillae covered by simple columnar or cuboidal epithelium, eosinophilic cytoplasm, round to oval nuclei situated basally, papillary fronds consisting of vascular stroma
CPP no necrosis, brain invasion or mitotic figures
CPCmarked cytological atypia, nuclear pleomorphism, loss of
polarity, high cellular density, frequent mitosis, necrosis, vascular proliferation, hemorrhage and brain infiltration
Atypical intermediate degree of nuclear atypia and mitotic figures
Imaging
homogenously enhancing tumor
vascular feeding pedicles
“frond like” solid tumor
associated hydrocephalus
CPCs demonstrate parenchymal invasion and peritumoral edema
Iso to hyperdense on CT with 25% showing calcification
Isointense on T1 and heterogenous on T2 MRI sequence
Management:
Extent of surgical resection – significant prognostic factor
Highly vascular tumor – perioperative blood loss add up to morbidity
Preresection chemotherapy used by some group to reduce blood loss
CPP and atypical form treated by gross total resection alone but CPC and if residual tumor in atypical form then adjuvant chemotherapy and craniospinal radiation
Hemangioblastoma..
WHO grade I
Highly vascular tumors seen in cerebellum and spinal cord
Most common posterior fossa lesion in adult but rare in pediatric group
Sporadic or as a part of von Hipple Lindau (VHL) familial syndrome
VHL – autosomal dominant(CNS hemangioblastomas, retinal angiomatosis, pancreatic cyst, renal cell carcinoma, pheochromocytoma and epididymal cyst)
VHL – germline mutation in VHL gene sensor of hypoxia induce vascular remodeling increased levels of VEGF highly vascular tumor
Typically well circumscribed cystic lesion with a small mural nodule abutting pia
But can vary from solid tumor to presence of central cyst
Cyst – hyperintense on both T1 and T2
Strong contrast enhancement of the solid component
Rx – GTR can be curative
If GTR can not be achieved then tumor control by gamma knife radiosurgery or fractionated radiotherapy
Dermoid/Epidermoid Cyst
Rare; <1% ; congenital non-neoplastic lesions arising from retained ectodermal and mesenchymal elements in neural groove during embryonic neural tube closure
Typically present in 3rd decade; rare in pediatric age group
Male predominance
Epidermoid commoner than dermoid (4-10:1); but dermoid commoner in children
Histologically benign but can present with mass effect, aseptic meningitis, infectious meningitis or neurovascular compression
Dermoid – contain both dermal and epidermal elements
typically midline in location
often associated with dermal sinus tract – typical location inion
associated with cutaneous stigmata of hair tufts, cutaneous angioma, and fluid leakage
may be associated with Klippel-Feil syndrome
Epidermoid:
contains epidermal elements
occur in more lateral locations, commonly in CPA
Often called pearly white tumors or cholesteatomas
Dermoids and Epidermoids – well circumscribed lesion with no edema and moderate mass effectHypo and hyperintense on T1 and T2
Epidermoid in CPA mimics Arachnoid cyst; Epidermoid exhibits DWI changes
Rx:
Surgical excision can be curative
Subtotal resection if densely adherent to neurovascular structures
Malignant degeneration to squamous carcinoma is reported but rare
Care not to avoid spillage of contents into the subarachnoid space during surgery aseptic meningitis
Surgical Management of Posterior Fossa tumors
Management of Hydrocephalus
83% of patients with posterior fossa tumor hydrocephalus30% of patients with HCP requires shunt after tumor removalOnly 6% will require shunt if ETV is done prior to removal of tumor
However, with this modality 70% of the children will have to undergo extra surgical procedure
J Neurosurg Pediatr. 2009 May;3(5):378-85. doi: 10.3171/2009.1.PEDS08298.Predicting postresection hydrocephalus in pediatric patients with posterior fossa tumors.Riva-Cambrin J1, Detsky AS, Lamberti-Pasculli M, Sargent MA, Armstrong D, Moineddin R, Cochrane DD, Drake JM.Riva-Cambrin et. Al Grading system for determining need for postoperative shunt diversion at 6 months:
age < 2yrs - 3 scorepapilledema – 1 scoreinitial degree of hydrocephalus – (moderate to severe) score 2tumor histological features – score 1presence of metastasis – score 3
Scores > or = 5 suggests high risk of developing hydrocephalus
This helps surgeon decide whether or not to do ETV
Currently: option of placing an occipital or “Frazier” burr hole during the surgical procedure for emergent decompression, should post op swelling occur
Surgical Approaches to Posterior Fossa Lesion
Prone position
Slight head rotation if lesion has lateral extension
Sitting posture: blood loss does not pool in the operative field but risk of air embolism
Midline suboccipital craniotomy
Splitting of inferior vermis lateral retraction of the dentate nuclei affects dentatonucleocortical projection cerebellar mutism
Modification: telovelar approach dissection of cerebellomedullary fissure to reach fourth ventricle without splitting the vermis
Telovelar approach
cerebellomedullary fissure opened by separating tonsillo uvular and tonsillomedullary spaces
Uvula retracted superiorly and tonsils laterally
Medullary velum and tela choroidea opened
Inferior roof of fourth ventricle exposed from aqueduct to obex
Opening of tela continued laterally to expose the foramen of Luschka
Posterior arch of C1 can be removed for larger working area and more lateral access
Suboccipital retrosigmoid approach
for lesions in the CPA
allows good visualization of lower cranial nerves and preserves hearing
curvilinear incision made 1-2 cm behind the mastoid
craniotomy performed medial to the sigmoid sinus
arachnoid over the cisterna magna and superolateral cerebellum opened to allow CSF drainage for cerebellar relaxation
care to monitor 7th CN
other more complex approaches like posterior petrosal or far lateral can be utilized in conjunction or separately
Surgical Adjuncts
Image guided surgery or neuronavigation – does not provide real time imaging
Intraoperative MRI
Intraoperative USG
Physiological mapping and monitoring
Mapping – physical stimulation of a brain region of interest awaiting for response; mapping of 4th ventricle for the facial, glossopharyngeal, vagal and hypoglossal nuclei to enhance surgical removal
Monitoring – ongoing activation and recording of neural circuits provide “warnings” of a breach in pathway integrity
50% drop in amplitude or an increased latency of 10% is indicative of pathway injury
Complications of Therapy
1. Cerebellar Mutism – complete absence of speech without impairment of consciousness; other symptoms – hypotonia, ataxia and emotional lability occurs in 25% patients resolution up to 6 months later damage to dentatothalamocortical tracts
2. Cerebellar cognitive affective syndrome
3. Neurocognitive side effects from radiation 20-30 points decrease in IQ with 36 Gy vs 10-15 points decrease with 23.4 Gy
4. Endocrine anomalies
5. Secondary Malignancy – Nonmelanoma skin cancers and benign meningioma
6. Mental health issues, unemployment and remaining single
Brainstem Gliomas
10-15% of primary pediatric intracranial neoplasm
2 decades ago – considered inoperable
Heterogenous group – some of which, amenable to long term survival
Predominantly pediatric entity with mean age of presentation – 7-9 yrs
Focal and exophytic types – low grade with much better prognosis than diffuse high grade
Diffuse Intrinsic Pontine Gliomas (DIPGs) – 60-80% of brainstem gliomas
Clinical Presentation
Dependent on anatomical location
DIPG rapidly progressive course of cranial neuropathies with
pyramidal tract and cerebellar signs
Focalisolated cranial nerve deficits and contralateral hemiparesis
spanning months to years
Cervicomedullarylower cranial nerve palsies, pyramidal tract signs, ataxia,
spinal cord dysfunction and nystagmus
Tectal tumors – hydrocephalus early due to location near the aqueduct
Diffuse Intrinsic Pontine Glioma
Most common brainstem tumor (60-80%)
Most devastating with median survival of 9 months
Rapid onset and progression
Triad of symptoms (cranial nerve palsies, long tract and cerebellar signs)
Hydrocephalus in advanced stages
Hypointense on T1 and Hyperintense on T2 with indistinct margins reflecting infiltrative nature
Variable Gadolinium enhancement
MRS to delineate it from demyelination, dysmyelination of NF1, encephalitis and radionecrosis
Due to natural history and malignant course very little clinical role for diagnostic biopsy
rationale: all DIPGs are high grade with poor prognosis and biopsy is associated with significant morbidity and mortality rates
May have role in future for targeted therapy
Mainstay Rx:
Radiation - 50 Gy
Hydrocephalus (majority – mild) – symptomatic relief with steroid administration
Palliative radiation – symptomatic relief in 75% but eventual recurrence
Focal Brainstem Tumors
Tectal Tumors
5% of brainstem lesions
Typically WHO grade I and II
Hydrocephalus, rapid deterioration and death – even with small size
Second aggressive subtype : > 2cm, invade adjacent tegmentum, thalamus or pons; demonstrate contrast enhancement
Common benign type: well circumscribed and nonenhancing
Signs:gait disturbances, ataxia, Parinaud syndrome, strabismus
Rx:Treatment of hydrocephalus and follow up with serial MRI
Some go for more aggressive approach – as 18-30% of tectal tumors progress
GKS – tumor stabilization
management of aggressive variant – debate: biopsy followed by radiotherapy vs complete surgical resection followed by radiation
Dorsally Exophytic Brainstem Tumors
10-20% of brainstem tumors
insiduous onset of headache, vomiting, ataxia and cranial nerve dysfunction (6th and 7th)
papilledema, torticollis and long tract signs
may protrude to 4th ventricle or if dorsolaterally exophytic then to CPA
hypointense T1 and hyperintense T2 with consistent tumor edges due to less infiltrative nature
predominantly pilocytic with occasional grade 2 and 3 and ganglioglioma
Most surgically accessible
Rx:
surgical debulking with serial imaging follow upRadio and chemotherapy – reserved for recurrenceNeuronavigation, DTI, Tractography, brainstem monitoring to maximize resection minimizing morbidity
Cervicomedullary Tumors
Slowly progressive crainal nerve palsies, pyramidal tract signs, ataxia, spinal cord dysfunction, or nystagmus
Lower cranial nerve deficits – dysphagia, nasal speech, nausea, vomiting, palate deviation, facial nerve palsy, head tilt, apnea, or irregular breathing patterns
Histology: pilocytic astrocytoma
Caudal 2/3rd of medulla to rostral portion of cervical spinal cord
Tumor less likely to penetrate the “anatomical barrier” – pyramidal decussating fibers, medial leminiscus, efferent fibers from the inferior olivary complex and inferior cerebellar peduncle
Rx:
Aggressive surgical resection because of well defined surgical plane
Risks: quadriparesis, sleep apnea, CN palsy, proprioceptive defect and spasticity
Radiation therapy can be utilized after surgery, although most wait for evidence of recurrence
Weiner et al (retrospective) – 5 yr PFS 60% and 89% alive even after 5 yrs
Other Focal Brainstem Tumors
<5% in other locations like medulla, midbrain, tegmentum
Anaplastic astrocytoma and GBM have also been described
Non neoplastic lesions – vascular malformations, demyelination and gangliosidoses
Brainstem Gliomas in Neurofibromatosis Type 1
Should not be confused with “unidentified bright objects” in NF1
Bright spots – common and disappears spontaneously
NF1 BSGs – more favorable prognosisSurvival rate – 90% at 5 years age
Role of Surgery in Brainstem Gliomas
Biopsy reserved when indeterminate findings in MRI
Biopsy – complication rate 10-30%
Surgery – role in focal tumors only 4 yrs OS and EFS of 87 & 59%
Perioperative ventilation, tracheostomy and gastrostomy in 41%; almost 80% have eventual complete recovery
Prone positioning
Anterior focal lesion – retrosigmoid approach
Dorsal focal – midline suboccipital approach – telovelar approach
General Principles
1. Identifying normal anatomy2. Identifying the most direct route to the tumor
(exploring tumor cysts, locating pial surfaces with discoloration from tumor bulge
3. Debulking the center prior to dissecting tumor margins
Neurophysiological monitoringBAER, SSEP, EMG, MEP, neuronavigation
Thank you!!