Progressive visual loss as the prominent clinical manifestation of a giant cauda equina paraganglioma

Clinical History

The patient presented with a 6-year history of progressive visual loss. Fundus examination demonstrated atrophy of the right optic disc and swelling of the left with a blurred rim and dilated retinal veins. Neurological examination was unremarkable except for symmetrically reduced deep tendon reflexes in the lower extremities.

Imaging Findings

The patient presented with a 6-year history of progressive visual loss. He had experienced transient obscuration of his vision several times. Atypical optic neuritis was diagnosed and he had received anti-inflammatory medication. His clinical history was otherwise unremarkable.
His condition progressively deteriorated, so that upon referral he was totally blind in the right eye and had visual acuity of 5/10 in the left. Fundus examination demonstrated atrophy of the right optic disc and swelling of the left with a blurred rim and dilated retinal veins. Neurological examination was unremarkable except for symmetrically reduced deep tendon reflexes in the lower extremities.
An MRI study of the brain revealed an empty sella and somewhat prominent subarachnoid spaces, considering his age. MRI study of the orbits disclosed on the left vertical tortuosity of the optic nerves and an enlarged perioptic subarachnoid space. On STIR images the right optic nerve demonstrated high signal. No abnormal contrast enhancement or other pathology was noticed.
The diagnosis of benign intracranial hypertension was suggested, although the typical symptoms were lacking. Therefore, a lumbar puncture was performed. An elevated CSF opening pressure of 65mmH2O and a high protein level of 3g/dl were found, thus confirming the presence of intracranial hypertension and directing the investigation towards the spinal canal. A lumbar MRI study showed an intradural lobulated mass, filling and expanding the canal, extending from the lower level of L3 to the lower level of S1. The mass was isointense with spinal cord on all pulse sequences and enhanced markedly after administration of contrast material. Prominent, intradural vessels superior to the mass and an entrapment cyst inferior to the mass were observed, as well.
The patient was operated on. A highly vascular, friable mass was found and a partial resection was performed, because the mass was adherent to the nerve roots. Pathological examination confirmed the diagnosis of paraganglioma.

Discussion

Paragangliomas are benign tumours arising from paraganglionic cells of the sympathetic nervous system. These tumours usually originate from the adrenal medulla. In about 10% of cases an extra-adrenal location is found, with the carotid body and jugular bulb being the most commonly affected sites. Spinal paragangliomas most often occur in the cauda equina region, as slow-growing intradural extramedullary highly vascular, encapsulated masses, originating from the filum terminale. Their clinical manifestations are nonspecific, including low back pain and leg radiculopathy; motor or sensory deficits and possible bladder dysfunction are late symptoms. Thus the diagnosis is usually delayed. When detected, they have to be distinguished from other tumours affecting the cauda equina such as myxopapillary ependymoma, haemangioblastoma, neurinoma or meningioma. Very rarely, cauda equina paragangliomas are hormone-excreting and they can be diagnosed based on the detection of increased neuropeptide production.

Most of the time the MRI features of paragangliomas lack specificity regarding the differential diagnosis from ependymoma. The characteristic salt and pepper appearance of paraganglioma, which has been described on T2 images in other locations, is encountered rarely in the cauda equina. The mass is usually isointense or hyperintense to spinal cord on T2 images, homogeneous or inhomogeneous, may show cystic components or a hypointense rim and invariably shows marked enhancement. The presence of serpiginous vessels around the lesion favours the diagnosis of paraganglioma, haemangioblastoma or vascular neurinoma.

The association of spinal cord tumours with increased intracranial pressure (ICP) is well known, but occurs uncommonly, with ependymoma being the cause in more than half of the cases. Several possible explanations exist, most of which are related to elevated CSF protein, derived from the tumour. Accordingly, it is proposed that CSF absorption is mechanically blocked primarily at the arachnoid villi or that stimulated basal arachnoiditis interferes with CSF flow. Aside from increased CSF protein level, recurrent subarachnoid haemorrhages and loss of the elastic reservoirs in the lumbar region of the spinal canal have been implicated as possible causes of increased ICP in these cases.
Papilloedema is the hallmark of increased ICP, although it can be caused by intrinsic disease (e.g. optic neuritis) as well. The meningeal covering of the brain normally continues into the orbit to surround the optic nerve. Direct transmission of increased ICP results in protrusion of the optic papilla into the globe. When the pressure exerted on the optic papilla is sufficiently chronic or severe, it causes permanent degeneration of the optic nerve, as occurred in this case. Several MR imaging characteristics of the brain and optic nerves indicating increased ICP have been described. In this patient there was a constellation of findings (vertical tortuosity of the optic nerves, enlarged perioptic subarachnoid space, empty sella and prominent intracranial subarachnoid spaces) which suggested the diagnosis of intracranial hypertension, despite the absence of headache, which almost invariably accompanies this condition. The negative neurological and intracranial imaging evaluation of the patient would have led to a diagnosis of idiopathic intracranial hypertension if CSF had not been examined.
This unusual case of a giant cauda equina paraganglioma manifesting with isolated papilloedema and visual disturbances, emphasises the need to exclude thoracolumbar intradural pathology in any case of unexplained increased intracranial pressure.

Differential Diagnosis List

Final Diagnosis

Visual loss due to cauda equina paraganglioma

URL:	https://www.eurorad.org/case/2114
DOI:	10.1594/EURORAD/CASE.2114
ISSN:	1563-4086