Bilateral optic pathway glioma in neurofibromatosis type1

Clinical History

Worsening of vision and headache in a two-year-old boy. On clinical examination multiple neurofibromas over the body, axillary freckling and 6 cafe au lait spots were noted, hence the patient was referred to our department with suspicion of neurofibromatosis type 1.

Imaging Findings

Bilateral optic nerves were swollen, tortuous and showed hyperintense signal in T2W (Fig. 6) sequence with areas of post-contrast enhancement (Fig. 7 a-c). Similar signal intensity change (Fig. 1 a, b) and intense post-contrast enhancement (Fig. 4)were noted in optic chiasma, optic tracts, left optic radiation and bilateral hypothalamic regions. There was no evidence of diffusion restriction (Fig. 2 a, b) and haemorrhage/calcification (Fig. 3) within. On MR spectroscopy with voxel placed over bilateral optic pathways showed elevated choline (Fig. 5 a, b) suggestive of bilateral optic pathway glioma.
Focal area of hyperintensity on T2W sequence was seen in the posterior aspect of medulla and upper cervical cord (Fig. 9 a, b) without significant post-contrast enhancement (Fig. 9 c, d) suggestive of low grade glioma.
Multiple areas of FLAIR hyperintense signal were noted in bilateral cerebellar lobes without post-contrast enhancement (Fig. 8 a, b) suggestive of focal areas of signal intensity (FASI).
There was expansion of spinal canal predominantly in the lumbar region with scalloping of posterior vertebral bodies (Fig. 10) suggestive of dural ectasia.

Discussion

Neurofibromatosis type 1, also known as von Recklinghausen disease, is one of the most common inherited CNS disorders, inherited tumour syndromes, multisystem neurocutaneous disorders, the most common phakomatosis, and a RASopathy.

Neurofibromatosis affects 1:2500-3000 individuals. [1] In half of the cases, the disease is inherited as an autosomal dominant condition. In the other 50% of cases the disease is due to a new mutation [3]. There is variable expression but 100% penetrance by 5 years of age. [3]

The NF1 gene locus is on chromosome 17q11.2 and the gene product is neurofibromin, which acts as a tumour suppressor of the Ras/MAPK pathway; inactivation of the gene thus predisposes to tumour development. [3, 5] For this reason, the disorder is classified as a RASopathy. [5]

The common CNS manifestations are FASI (focal areas of signal intensity) [2], optic nerve/ optic pathway gliomas, sphenoid wing dysplasia, bupthalmos, dural ectasia, moya moya phenomenon (rare), dural calcification and lambdoid suture defect.

In our case provisional diagnosis of a neurocutaneous disorder was made clinically. MRI of brain and whole spine with gadolinium contrast and single voxel MR spectroscopy was done for confirmation of the specific syndrome, assessment of disease progression and to rule out the possibility of another disease.

Bilateral enlarged, tortuous optic nerves with altered signal intensity (hyperintense in FLAIR and T2W sequences) and significant post-contrast enhancement is characteristic of optic nerve glioma. In our case there was extensive involvement along the bilateral optic pathway (left>right) and also involvement of medulla and upper cervical cord. There were other common manifestations of CNS neurofibromatosis type1 like FASI and dural ectasia as already described.

Bilateral infiltrating optic pathway glioma has a poor prognosis. [4] The child underwent treatment with chemotherapy and a repeat scan of brain and cervical spine after two months to assess treatment response. On 2 months repeat scan no significant shrinkage of tumour size/volume was noted.

Differential Diagnosis List

Final Diagnosis

Bilateral optic pathway glioma with cervicomedullary glioma in neurofibromatosis 1

URL:	https://eurorad.org/case/15611
DOI:	10.1594/EURORAD/CASE.15611
ISSN:	1563-4086