BRAIN STEM GLIOMA

1. D R H I M A N S H U S O N I
BRAIN STEM GLIOMAS

2. Introduction
 Intrinsic brainstem tumors are common in
childhood.
 Comprise – 20 % all pediatric brain tumors
 In pre-CT era, all tumors between thalamus and CM
jn were called brainstem gliomas.
 Tradiational therapy consisted of
 Biopsy  irradiation  chemotherapy
 Little success was met with these therapies.

3. Classification
 Numerous classifications exists
 Basically two categories
 FAVORABLE PROGNOSIS
 Focal, discrete, exophytic lesions
 Mainly pilocytic astrocytomas
 Amenable to total excision
 POOR PROGNOSIS
 Diffusely infiltrative, relentless growth, resistance to CT, RT
 Mainly fibrillary, anaplastic astrocytomas, GBM

4. Site, imaging, pathology classification
LOCATION IMAGING HISTOPATHOLOGY
Midbrain Tumor Diffuse Gliomas
Low Grade / Benign
Tumors
Tectal Tumor Intrinsic Gliomas Pilocytic And Grade II
Pontine Glioma Pencil Gliomas High Grade Tumors
Focal Medullary Tumor Exophytic Gliomas Grade III, IV
Cervicomedullary Tumor Dorsal
Ventral
Lateral
Focal Tumors
Cystic Tumors

5.  Most commonly used classification
includes
 Focal, diffuse, exophytic, tectal plate and
CM tumors
 For practical purposes, two
categories
 Focal – discrete, exophytic
 Classic – diffusely infiltrative lesions
 “intrinsic” gliomas – within the
brainstem axis, surrounded by
normal parenchyma.

6. “intrinsic” glioma classification
 Expanding variety
 Well delineated on C – MRI
 Posteriorly, posterolaterally, ventrolaterally
 Slow progression of deficits
 Motor function preserved
 Infiltrating diffuse variety
 Margin betn tumor and parenchyma not well defined
 Short history and rapid progression
 Ventrally located tumors
 “very difficult to access”
 Should not be operated upon

9. PATHOLOGY
 Mostly astrocytomas, infiltrative tumors, fibrillary
type, similar to diffuse cerebral astrocytomas
 Diffuse hypertrophy of pons (symmetrical
enlargement)
 Expanding lesion encroaches posteriorly and
superiorly upon the fourth ventricle.
 Medulla is often spared, sometimes, may arise from
medulla and spread to upper cervical region.

10.  Diffuse replacement of nerve tissue by small and
large astrocytic cells (stellate, pilogytic and
gemistocytic), randomly dispersed or arranged in
groups.
 Cellular heterogeneity, anaplasia, necrosis and
endothelial proliferation as seen in GBM.
 Based on macroscopic appearance, divided into
following categories :
 Dissuse, focal, cervicomedullary, cyctic, exophytic and tectal
plate gliomas.

11.  Diffuse
 Short history, multiple cranial nerve palsies with long
tract signs
 MRI diagnositic
 Invariably malignant, advised RT / CT
 Surgery is not indicated
 Biopsy is not advised
 Focal
 Commonly involved medulla, long history
 Focal deficits – VI , VII palsies
 Low grade astrocytomas
 Amenable to surgical excision

12.  Cervicomedullary tumors
 Low grade astrocytomas, gangliogliomas
 Amenable to radical excision
 Well defined margins
 Cystic tumors
 Low grade pilocytic astrocytomas
 Amenable to radical excision
 Exophytic tumors
 Exophytic growth – ventrally, laterally into the CP angle, or
dorsally into the fourth ventricle
 Dorsal tumors have best prognosis and amenable to surgery.

13.  Tectal plate gliomas
 Uncommon in pediatric age group.
 Main feature is hydrocephalus
 C – MRI diagnostic
 Managed by VP shunt, observation, RT in case of increase in size.
 Radiosurgery has been introduced.
 ETV or aqueductal stenting – better alternative.

14. CLINICAL FEATURES
 Characteristic features of an intrinsic brainstem
neoplasm are
 Internuclear ophthalmoplegia
 Horner’s syndrome
 Weber’s syndrome – ipsilateral III nerve paresis, contralateral
hemiparesis
 Cranial nerve nuclei involvement – VI, VII palsies
 Vomitting is a common symptom – area postrema
 Ataxia – cerebellar peduncles involvement
 Motor weakness – pyramidal tract involvement

15.  Squint , EOM palsies
 Internuclear ophthalmoplegia – MLF involvement
 Facial weakness, dysarthria, dysphagia
 Features of raised ICP
 tectal plate tumors – early raised ICP
 CM tumors – lower CN palsies with pyramidal tract
signs
 Radical surgery possible with little morbidity
 Mostly low grade gliomas

16.  Pons tumors – infiltrative, malignant
 CN palsy, pyramidal signs, ataxia
 Progress without raised ICP
 Poor prognosis, survival < 2years
 Surgery not helpful

17. D/D and special subgroups
 Diffuse brainstem enlargement with NF – 1
 MRS can differentiate
 NA marker preserved in NF – 1, lost in diffuse gliomas
 Benign brainstem gliomas – Hoffman et al
 Dorsally exophytic transependymal benign brainstem gliomas
 Longer history, 75% have hydrocephalus
 Ataxia common, CN deficits, LT signs rare
 Amenable to surgery
 Focal midbrain astrocytomas
 50% tectal plate 50% tegmentum, 83% have hydrocephalus
 Perinaud syndrome – dorsal midbrain syndrome

18. IMAGING
 C – MRI
 Assess for location, focality, signal intensity, extent of infiltration,
brainstem enlargement, cyst, necrosis, hemorrhave or exophytic
component
 Characterise and classify the tumor
 Focal / diffuse / CM / exophytic type
 Categorise as – intrinsic / exophytic
 Exophytic – whether expanding / diffuse infiltrative / pure ventral
 Exophytic, cystic, expanding should be subjected to
surgery

19. SURGICAL APPROACHES
 Depent on location and projection of tumor
 Pons, medulla and CM tumors
 Midline suboccipital craniectomy
 Prone position
 With/out vermian splitting
 Midbrain
 Midline suboccipital craniectomy / vermian splitting approach
 Sitting position
 Lateral exophytic
 Paramedian / CP angle approach

20. INTRA OPERATIVE MONITORING
 Rhomboid fossa - “no-man’s land”
 Two types of monitoring methods used
1. Intraoperative motor nucleus mapping
2. Continuous intraoperative electromyographic
monitoring

21. INTRA OPERATIVE MOTOR NUCLEUS MAPPING
 During motor mapping in the brainstem, electrical
stimulation of the nucleus elicits continuous motor
action potentials (CMAP)
 Tongue muscles – hypoglossal / vagal triangle
 Facial muscles, lateral rectus – facial colliculus
 Extraocular muscles – ocular motor pathways

22. CONTINUOUS INTRA OP EMG MONITORING
 Continuous EMG can provide information about
respective motor nerve nuclei.
 Reliable wasy to identify exact location of various CN
nuclei to plan the incision on brainstem
 For dorsal lesions
 Electrodes connected to orbicularis oris, oculi, tongue muscles
 Intermittent or continuous stimulus of 0.1 – 1 mA used

23. SURGICAL PRINCIPLES
 Focal cystic tumors –
 decompression of the cyst, farily easy procedure, f/b RT
 Dorsally exophytic tumors
 Tumor is shaved off flush with the floor of the fourth ventricle
 Tectal plate tumors
 Shunting procedure f/b RT
 Once fourth ventricle floor is reached
 Look for “bulges “ or “ discoloration”
 Direct stinulation and mapping of CN nuclei
 If no exophytic component, incise in a “safe area”, as small,
longitudinal, nearest to the tumor, away from nuclei, usually
dorsolateral sulcus lateral to the CN nuclei

24.  Use tisue vaporiser, as there is minimum heat
dissipation to the surroundings
 Aspirate the cyst before approaching the solid tumor
 Use micro-tip ultrasonic aspirators
 Tumor rim should be left behind, if no plane seen.
 Start inj methylprednisolong before making a
brainstem incision and continue for 24-48 hours as
30 mg’/kg for HR 1, f/b 5.4 mg/kg/hr

25. MANAGEMENT OF DIFFUSE TUMORS
 Worst prognosis, surgival < 18 months
 Varied histology in different tumor areas, hence
biopsy is not reliable for diagnosis
 Direct radiiotherapy – 55 Gy to the tumor area,
weekly dose of 800-1000cGy

26.  Thank you