There is no universally accepted staging system for visual pathway and hypothalamic gliomas. They are low-grade astrocytomas that grow slowly and may occur anywhere along the optic tracts. Visual pathway gliomas are found with increased frequency in patients with neurofibromatosis. The major clinical symptoms are visual. Tumors may also arise in the hypothalamus; in large infiltrating lesions, distinctions between optic and hypothalamic tumors are often artificial and of little clinical importance. In infants and young children, hypothalamic gliomas may result in the diencephalic syndrome, which is manifested by failure to thrive in an emaciated, seemingly euphoric child. Such children may have little in the way of other neurologic findings, but can have macrocephaly, intermittent lethargy, and visual impairment.[1] Because the location of these tumors makes a surgical approach difficult, biopsies are not always done. This is especially true in patients with neurofibromatosis type 1 (NF-1).[2] Visual pathway and hypothalamic gliomas usually spread contiguously, though subarachnoid dissemination has been reported.[1,3] Evaluation should include neuro-ophthalmological testing to carefully monitor the patient for the visual effects of tumor progression that may not be evident using computed tomography or magnetic resonance imaging. Visual-evoked responses have not, as yet, been shown to be more sensitive than clinical examination in patients with visual pathway gliomas, even in young children.

References:

1. Perilongo G, Carollo C, Salviati L, et al.: Diencephalic syndrome and disseminated juvenile pilocytic astrocytomas of the hypothalamic-optic chiasm region. Cancer 80 (1): 142-6, 1997.
2. Pollack IF, Mulvihill JJ: Special issues in the management of gliomas in children with neurofibromatosis 1. J Neurooncol 28 (2-3): 257-68, 1996 May-Jun.
3. Mamelak AN, Prados MD, Obana WG, et al.: Treatment options and prognosis for multicentric juvenile pilocytic astrocytoma. J Neurosurg 81 (1): 24-30, 1994.