Case No. :	24
Month :	December
Year :	2000
Contributor :	Dr. Hemant Parmar

Case report |Radiological Features | Discussion

Case report:

A two year old child, weighing 15 kg and measuring 93 cm in height, presented with proptosis and decreasing vision in both eyes since last 4-5 months. On examination, café-au-lait spots were found on the body. The head circumference had increased and milestones were slightly delayed. Fundoscopic examination revealed bilateral papilledema. There was no significant family history or any sibling affection. MRI of the brain was performed.

Radiological Features:

MRI reveals kinking and fusiform enlargement of both optic nerves with ectasia of the perineural sheaths. These appeared hypointense on T1 and hyperintense on T2WI (Fig.1). The optic chiasm was also involved. The optic tracts, geniculate bodies and optic radiations revealed similar signal intensities (Fig.2). Hyperintense areas were present within the hypothalamus, bilateral thalami, basal ganglia, cerebral peduncles, temporal lobes and cerebellar hemispheres (Fig.3). The pituitary stalk was slightly thickened but the gland revealed normal dimensions and signal characteristics.

Discussion:

Neurofibromatosis-I (NF-1) (autosomal dominant inheritance) or von Recklinghausen's disease has an incidence of about 1:2000 to 1:3000. 15 to 35 % of the patients with NF-1 have optic nerve gliomas .It usually presents within the first decade with proptosis and visual loss . Optic nerve atrophy is more common than papilledema. Signs and symptoms of increased intracranial tension, hypopituitarism, obesity, dwarfism, diabetes insipidus and precocious puberty may occur with invasion of the third ventricle and hypothalamus. Our patient was obese and also had involvement of the hypothalamus on MRI.

Imaging is necessary in patients with NF-I as two-thirds of the optic gliomas are asymptomatic and not evident on clinical examination.. Ten to twenty of patients with optic nerve gliomas have bilateral disease. Ectasia of the optic nerve sheath is common in NF1 and appears as irregular, CSF-filled spaces around the nerves. Chiasmatic gliomas usually involve the optic tracts but only uncommonly involve the optic radiations and are associated with a poor prognosis. Also associated are hyperintense areas on T2WI within the hypothalamus, thalamus, basal ganglia and/or brainstem. Edema, atypical proliferation of the glial cells and extension of the infiltrating gliomas have been proposed to explain these hyperintensities. Tumour can be inferred when mass effect and / or contrast enhancement is detected, along with hyperintensities

In one series of twenty-one patients with NF-I, there was involvement of both optic nerves as well as chiasma in five patients and geniculate bodies in four cases. However, involvement of optic radiations was seen in only one patient. In another series of 53 cases, there was found simultaneous optic nerve and chiasmatic gliomas in ten patients. Of these, only four optic chiasmatic gliomas were more than 1.5 cm in size, as in the present case. Involvement of optic radiations was seen in only three cases. Our case shows bilateral involvement of the optic radiations. Extensive optic tract gliomas with extension beyond the geniculate bodies and involvement of the optic radiations are very uncommon.