Discussion:
Paragangliomas are tumors whose embryological origins arise from autonomic nervous system (3). Normally, paraganglionic cells migrate along the neural tube. Thus, paragangliomas are a result of dysfunction of embryonic paraganglia, whether related to cell migration or their non-regression (2). Paragangliomas could be found in adrenal and extra-adrenal tissues. Extra-adrenal tumors can be categorized into sympathetic and parasympathetic types (4). The sympathetic paragangliomas have usually the possibility to be hormone-secretant, mostly cathecolamines (Dopamine, Noradrenaline and Adrenaline) (5). Parasympathetic paragangliomas tend to be non-secretory. These forms could result from a local differentiation from tissues that do not derive from the neural crest. Furthermore, the participation of the ependymal cells in their development cannot be excluded, which explains the non-secretory type (1).
In the central nervous system, nearly 80% of paragangliomas occur in the head and neck. They are typically parasympathetic and arise from the glomus jugularis or the carotid body. At level of cauda equina or filum terminale, they are very rare representing 2–4% of cases (2).
The highest prevalence for cauda equine paragangliomas commonly sets around the fourth and fifth decades of life. A male predominance is usually noticed. It is admitted that they are sporadic neoplasms, but nearly 1% of cases are autosomal dominant (5).
Most of the patients present with lumbar or radicular pain. Nevertheless, other clinical features may be found: motor or sensitive deficit, and genital or sphincter disorder. Symptoms of sympathetic secretion related to catecholamine are uncommon (2). There is no significant correlation between the tumour dimension and the duration of clinical symptomatology onset. In the literature, there would be only two cases in which an acute neurologic deficit was found, related to an intratumoral hemorrhage (1).
MRI is the gold standard for both the diagnosis and the follow-up of paragangliomas of cauda equina or filum terminale. Typically, they appear isointense to the conus medullaris on T1-weighted images (WI) and hyperintense on T2-WI, with homogenenous or heterogeneous enhancement after gadolinium injection which is is related to the important vascular supply for the tumor (3). However, these tumors do not have any pathognomonic features. This is why they are frequently misdiagnosed, as they lead to confusion with other tumors as schwannomas, ependymomas, meningioma, teratoma, and hemangioma (2). A serpiginous flow void from vessels seen on the upper pole of the lesion, and signs of intra or peritumoral bleeding can be present.
Histologically, paragangliomas are graded as WHO Grade I tumors. They are slow-growing benign tumors comprised of two cell types, spindle shaped sustentacular cells and chief cells. S100 staining is positive in sustentacular cells, but it is not specific as a possible positivity can be found in ependymomas. Ependymal cells are GFAP positive whereas GFAP staining is negative in neoplastic cells of paragangliomas (4). Mature ganglion cells are contained in nearly half of the paragangliomas of cauda equina.
Total surgical excision is presented to be the best option to achieve greater chance of cure and to reduce recurrences (5). Several authors queried this option because the relatively benign natural history can make from expectation a reasonable option in asymptomatic cases. Peroperative, paragangliomas are most often intradural and extramedullary. They appear well encapsulated, purple, friable and often haemorrhagic. The main technical difficulty is dense adhesion to nerve roots, which can make surgical excision hard without impairing the roots (2). The outcome is overall excellent when complete excision of the mass is performed. Nevertheless, some authors recommend a long-term follow-up due to a possibility of recurrence (1–4%) (2). When only subtotal resection is performed, 10% of the tumours recurred within one year following surgery. In the case of incomplete resection, radiotherapy is recommended with a significant effect on recurrence (3).