Brain stem gliomas are classified according to their location, radiographic appearance, and histology (when obtained). Brain stem gliomas may occur in the pons, the midbrain, the tectum, the dorsum of the medulla at the cervicomedullary junction, or in multiple regions of the brain stem. The tumor may contiguously involve the cerebellar peduncles, cerebellum and/or thalamus. The majority of childhood brain stem gliomas are diffuse, intrinsic tumors that involve the pons (diffuse intrinsic pontine gliomas [DIPG]), often with contiguous involvement of other brain stem sites.[1,2,3,4] The prognosis is poor for these tumors. A prognostically more favorable subset of tumors are focal pilocytic astrocytomas. These most frequently arise in the tectum of the midbrain, focally, within the pons, or at the cervicomedullary junction, and have a far better prognosis than diffuse intrinsic tumors.[2,3,5,6,7]

Primary tumors of the brain stem are most often diagnosed based on clinical findings and on neuroimaging studies,[8] and there is a substantial amount of histologic variability within an individual tumor. DIPGs are generally fibrillary astrocytomas. However, histologic confirmation is usually unnecessary. Biopsy specimens of intrinsic brain stem gliomas may be misleading because of sampling error. Biopsy or resection may be indicated for brain stem tumors that are not diffuse and intrinsic. New approaches with stereotactic needle biopsy may make biopsy safer.[9]

References:

1. Cohen ME, Duffner PK, Heffner RR, et al.: Prognostic factors in brainstem gliomas. Neurology 36 (5): 602-5, 1986.
2. Albright AL, Guthkelch AN, Packer RJ, et al.: Prognostic factors in pediatric brain-stem gliomas. J Neurosurg 65 (6): 751-5, 1986.
3. Halperin EC, Wehn SM, Scott JW, et al.: Selection of a management strategy for pediatric brainstem tumors. Med Pediatr Oncol 17 (2): 117-26, 1989.
4. Freeman CR, Farmer JP: Pediatric brain stem gliomas: a review. Int J Radiat Oncol Biol Phys 40 (2): 265-71, 1998.
5. Epstein F, McCleary EL: Intrinsic brain-stem tumors of childhood: surgical indications. J Neurosurg 64 (1): 11-5, 1986.
6. Edwards MS, Wara WM, Ciricillo SF, et al.: Focal brain-stem astrocytomas causing symptoms of involvement of the facial nerve nucleus: long-term survival in six pediatric cases. J Neurosurg 80 (1): 20-5, 1994.
7. Pollack IF, Pang D, Albright AL: The long-term outcome in children with late-onset aqueductal stenosis resulting from benign intrinsic tectal tumors. J Neurosurg 80 (4): 681-8, 1994.
8. Albright AL, Packer RJ, Zimmerman R, et al.: Magnetic resonance scans should replace biopsies for the diagnosis of diffuse brain stem gliomas: a report from the Children's Cancer Group. Neurosurgery 33 (6): 1026-9; discussion 1029-30, 1993.
9. Cartmill M, Punt J: Diffuse brain stem glioma. A review of stereotactic biopsies. Childs Nerv Syst 15 (5): 235-7; discussion 238, 1999.