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Q1: Based on history and clinical examination what is the differential diagnosis?
Differential diagnosis for raised intracranial pressure with cauda equina syndrome include entities with lesions at multiple sites such as:
Malignant meningitis, particularly lymphoma with root lesions.
Q2: What are the investigations required?
Imaging of the craniospinal axis and cerebrospinal fluid (CSF) analysis are required for diagnosis. In our case, magnetic resonance imaging of the brain showed no expanding mass lesion, except for a small left parietal arachnoid cyst. CSF analysis was then done by lumbar puncture. The fluid was xanthochromic with an opening pressure of 30 cm H2O. CSF protein was 30 g/l, glucose 5.4 mmol/l, white blood cell count 40 × 106/l, and red blood cell count 160 × 106/l. This was suggestive of a CSF block in the spinal canal.
Magnetic resonance imaging of the spine showed a intradural, extramedullary heterogeneously enhancing mass lesion at the D11–L2 level, which was hypointense on a T1 weighted image and hyperintense on a T2 weighted image (figs 1 and 2).
Q3: What are the causes of bilateral papilloedema without an expanding intracranial mass lesion?
The causes of bilateral papilloedema without an intracranial expanding mass lesion include:
Collagen vascular diseases.
Idiopathic intracranial hypertension.
Q4: What are the mechanisms/processes which lead to raised intracranial pressure in patients without intracranial mass lesions?
Bilateral papilloedema and diplopia without an expanding intracranial mass lesion in a patients with spinal cord tumours have been reported in the past. Raised CSF protein (causing delayed absorption of CSF due to increased viscocity) and leptomeningeal inflammation (probably due to the toxic effect of protein secreted by the spinal cord tumours) are the proposed mechanisms for the raised intracranial pressure in patients with spinal cord tumours.
This patient underwent excision of the tumour and the biopsy was reported as a myxopapillary ependymoma. After this her raised intracranial pressure and lateral rectus palsy resolved. Bilateral papilloedema and diplopia without an expanding intracranial mass lesion have been reported in patients with spinal cord tumours. Common spinal tumours associated with raised intracranial pressure are ependymoma, schwannoma, meningioma, neurofibroma, and glioma.3,5 Common clinical features seen among the patients in the previous reported cases include2–5:
Raised CSF protein.
Young, female patient.
So far no definite cause has been explained for the raised intracranial pressure in these cases. Whether it is because of the tumour itself or because of the effects of the proteins secreted by these tumours into the CSF is not clear.
Raised CSF proteins causing increased viscocity could delay CSF absorption and in turn cause raised intracranial pressure.6 Clogging of the pores of the semipermeable membrane of the arachnoid villi by large protein molecules could also retard CSF absorption.7 Raised CSF pressure causes increased pressure on the subarachnoid veins and leads to transudation of substances and further elevation of protein.
Consider a spinal tumour in a patient with normal cranial imaging and a diagnosis of presumed benign intracranial pressure.
Venous stasis by the tumour compression of spinal or medullary venous plexuses causing an unfavourable transarachnoid villous hydrostatic pressure is another proposed mechanism.8 Leptomeningeal inflammation due to the toxic effect of CSF protein causing compromise of CSF absorption is another possible mechanism for raised intracranial pressure.9
The spinal canal acts as an elastic reservoir for CSF. With normal changes in physiological cerebral blood flow, the ability of the CSF to flow into and out of the spinal canal is thought to be important in maintenance of a constant intracranial volume. By compromising this system spinal tumours may in fact reduce the capacity of this resorvoir and cause papilloedema.10
Spinal ependymoma with intracranial hypertension.