FINAL DIAGNOSIS: -- GANGLIOGLIOMA
Gangliogliomas are benign tumors composed of neurons and glia, the majority of which arise in the cerebral hemispheres, especially the temporal lobes. Patients commonly present with a history of chronic seizures(1, 2). They have an equal sex distribution and the majority are detected in individuals in the first 3 decades (3). Their incidence in the spinal cord accounts for approximately 1% of all spinal tumors (4). In this location, their extent is highly variable including reports where the entire cord has been involved (5). Gangliogliomas usually present with a subacute to chronic clinical course owing to their very slow growth. Malignant examples and malignant transformation are well documented but fortunately rare events (4, 6). Gross total resection is the treatment of choice with adjuvant therapy (radiation) reserved for anaplastic examples (1). The prognosis for a tumor that has been completely resected is excellent (1, 7). Although spinal examples carry a higher quoted relative risk of recurrence (3.5X) than their cerebral counterparts, 5 and 10 year survivals are still favorable (89% and 83% respectively)(7). Clinical outcome is best correlated with the preoperative extent of neurological deficit (7).
Spinal cord gangliogliomas are rare but pathologically identical to those arising at other sites in the CNS. As with other primary tumors, their border with surrounding CNS is indistinct. Features such as perivascular lymphocytic infiltrates, cyst formation and calcification are typical. The key components of these tumors are a highly variable mixture of glia and neurons. The glial component is most often astrocytic but may be predominantly oligodendrocytic or mixed and may show variable anaplasia. Mitotic activity is unusual. The neurons of gangliogliomas are notable for several typical architectural features. They are individually randomly oriented in a fibrillary matrix. Their size and shape are highly variable with frequent multinucleation and large bizarre forms. Finally, the neuronal component is often irregularly clustered and may be lobulated by bundles of reticulin. Immunohistochemistry demonstrates neuronal expression of NSE, NF, SYN, microtubule associated proteins, class III beta tubulin and chromogranin.
The etiology of gangliogliomas is controversial as is their biological potential. Some lesions display neoplastic features including the potential to enlarge and behave in a malignant fashion. On the other end of the scale, quiescent examples followed for many years with no obvious neoplastic potential suggest a more hamartomatous nature. Furthermore, their association with cortical dysplasia(8) reminds us of the overlap between development and control of cellular proliferation.
At the time of his review, Hamburger found a total of 66 reported cases of spinal cord gangliogliomas (3). There have been 3 previous cases of gangliogliomas restricted to the conus medullaris (9-11) all of which underwent a gross total resection with no reported recurrence. Our patient's neurological deficit remains unchanged 15 months post-resection with no evidence of recurrence.
Contributed by Sharyn J Smith, MD, Steven P Lownie, MD, Neil Duggal, MD and Robert R Hammond, MD