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Extrinsic cerebral venous sinus obstruction resulting in intracranial hypertension

Abstract

We report the case of a 70-year-old man reporting with headache and visual disturbances who was being treated for prostate cancer. Investigations showed him to have intracranial hypertension caused by venous sinus obstruction. Patients with metastatic disease and raised intracranial pressure in the absence of focal signs should be considered as possible cases of venous outflow obstruction.

  • intracranial hypertension
  • venous sinus thrombosis
  • malignancy

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A 70-year-old man presented with a 1-month history of progressive generalised headache, worse in the morning and on straining, and a 1-week history of visual obscurations. He was otherwise well, although he was taking goserelin for carcinoma of the prostate, diagnosed in 1994 on the basis of a raised prostate-specific antigen and malignant-feeling prostate. On examination visual acuity was decreased to 6/24 in the right eye and 6/36 in the left eye. Both fundi were severely papilloedematous. The remainder of the neurological and general examination was normal.

Baseline haematology and biochemistry, including calcium levels, were normal. Erythrocyte sedimentation rate was 12 mm/h. Serum immunoglobulins and electrophoresis were normal. Cranial computed tomography showed midline expansion and sclerosis of the occipital bone. Magnetic resonance imaging (MRI) confirmed midline occipital enlargement with loss of normal diploic marrow signal (figure 1). Axial images showed extrinsic compression of the superior sagittal sinus superior to the torcula (figure 2) which was confirmed on venous magnetic resonance angiography (MRA) (figure 3). A bone scan showed several metastases including the lesion in the occiput. He proceeded to have a lumbar puncture to confirm the clinical diagnosis of intracranial hypertension, to treat it by removal of cerebrospinal fluid (CSF), and to look for an underlying cause, such as malignant meningitis. The opening CSF pressure was 37 cm. The CSF was acellular with a protein content of 0.23 g/dl. He was treated with high-dose dexamethasone and repeated lumbar punctures prior to radiotherapy to his occiput. His visual acuity returned to 6/6 with resolution of his headaches. He subsequently developed further headaches and underwent surgery. The malignant deposit was peeled off the dura with visible re-expansion of the underlying venous sinus. Histology was very suggestive, but not diagnostic of a prostatic metastasis. The patient's headaches promptly resolved.

Figure 1

Sagittal short TE/short TR (T1 weighted) MRI showing midline expansion of the occipital bone (arrows). The normal high signal intensity marrow within the diploic space has been replaced by low signal intensity tissue

Figure 2

Transaxial long TE/long TR (T2 weighted) MRI at the level of the occipital lobes. There is extrinsic compression of the superior sagittal sinus flow void (arrow) by the midline occipital bony expansion

Figure 3

Maximum intensity projection image from a coronally acquired 2-dimensional time-of-flight venous MRA sequence. The extrinsic compression of the superior sagittal sinus is confirmed (arrow). There is also absence of flow signal within the left transverse dural sinus (broad arrow)

Discussion

Idiopathic intracranial hypertension, as benign intracranial hypertension is now known, is believed to be due to a problem with CSF resorption into the arachnoid granulations which project into the venous sinuses. It may be classified as primary or secondary. The primary cases may occur in association with a variety of medical conditions, such as hyperparathyroidism, or idiopathically. Secondary cases may be due to altered CSF composition such as high protein states, or due to interference with the venous outflow. The commonest cause of venous outflow obstruction is venous sinus thrombosis. These cases may present with headache and papilloedema in the absence of focal signs.1 Much less well recognised is venous obstruction from extrinsic compression causing a similar syndrome.

Plant et al 2 presented two similar cases. In their first case a plasmacytoma was peeled off the dura at surgery resulting in visible re-expansion of the superior sagittal sinus. Their second case was of metastatic Ewing's sarcoma compressing the torcula. Other cases reported have included neuroblastomas, breast cancer and meningiomas.3-5Gironell et al 6 have recently reported midline occipital non-Hodgkin's lymphoma causing non-thrombotic superior sagittal sinus occlusion. The vast majority of cases have compression of the terminal superior sagittal sinus and torcula. There appears to be no particular vascular anatomical reason why metastases should concentrate here but more likely reflects the fact that metastases elsewhere in the skull are less likely to become symptomatic. Presumably this is because lesions here result in raised pressure along the entire length of the superior sagittal sinus. This would therefore affect the arachnoid granulations to the maximum extent. It is important to note the absence of focal signs in these patients.

References

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