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).