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Brainstem glioma

Dr Frank Gaillard et al.

Brainstem gliomas consist of a heterogenous group which vary greatly in histology and prognosis. It should be noted however that if otherwise not specified the term brainstem glioma usually refers to the most common histology, the diffuse brainstem glioma.

Epidemiology

Brainstem gliomas account for approximately 25% of all posterior fossa tumours and are most common in children between 7 and 9 years of age 5. There is no recognised gender or racial predilection.

Brainstem gliomas are also recognised in adults, although they are rare accounting for only 2% of adult brain tumours 7. They typically occur in younger adults (third and fourth decade) and tend to be of low grade (WHO I or II) 7.

Clinical presentation

Although the exact presentation will vary according to location and size of the tumour, in general patients will exhibit a combination of  4:

The duration of symptoms is usually much shorter in diffuse gliomas, in which the history is typically very short (a few days) 4. Additionally, diffuse gliomas more frequently have multiple cranial nerve palsies.

Classification

The most frequently used classification system is to divide these tumours into 4 types 5:

  1. diffuse brainstem glioma
  2. focal brainstem glioma
  3. (dorsally) exophytic
  4. cervicomedullary
    • probably an artificial group made up of the downward extension of true brainstem gliomas or upward extension of upper cervical cord intramedullary spinal cord tumours 5.
Associations

neurofibromatosis type 1

Location

As a general rule mesencephalic tumours tend to be of a lower grade than those in the pons and medulla 3.

  • pontine
  • mesencephalic
  • medullary
    • least common location
    • includes focal dorsally exophytic, focal, diffuse and cervicomedullary junction variants
    • cervicomedullary junction tumours usually represent upper cervical tumours extending superiorly.
    • most common location for NF1 associated tumours

Histology

  • diffuse astrocytoma
    • usually fibrillary astrocytomas
    • WHO grades II-IV
    • grade does not impact on prognosis, and thus biopsy is usually not necessary
  • focal glioma
  • (dorsally) exophytic glioma 4,6
    • low grade astrocytoma 
    • ganglioglioma
  • NF1 associated brainstem glioma
    • seen in up to 9% of NF1 patients
    • most frequently seen in the medulla
    • appears similar to a sporadic focal brainstem glioma but has an even better prognosis, with little if any progression

Radiographic features

MRI

MRI is the imaging modality of choice. The appearance will vary with the tumour type, thus please refer to individual articles. 

DSA / angiography

May show anterior displacement of the basilar artery

Treatment and prognosis

Again, both treatment and prognosis are significantly influenced by tumour type, morphology and location. Radiation is a key part of treatment.

As a general rule, dorsal exophytic tumours and cervicomedullary tumours tend to do best with surgery, whereas surgery has no role in the management of diffuse brainstem gliomas. 

Prognosis
  • diffuse
    • terrible prognosis
    • 90-100% patients die within 2 years of diagnosis 6
  • focal (tectal glioma)
    • excellent long term survival with CSF shunting (essentially benign lesions)
  • focal (other)
    • good long-term prognosis with surgery
  • (dorsally) exophytic tumours
    • good long-term prognosis with surgery

Differential diagnosis

General imaging differential considerations include

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