HSC Section 8_April 2017

G. Madani, S.E.J. Connor

from the thyroid may contain flow voids mimicking a glomus tumour. 18 Haemangiopericytoma is a rare vascular tumour associated with PT. Its avid enhancement character- istics are similar to meningioma and these tumours may be indistinguishable on imaging. 19 Other rare neoplastic causes of PT include ossifying haemangiomas of the facial nerve and cavernous haemangiomas. 11 Dural arteriovenous fistulae (dAVFs) account for only 10 e 15% of all intracranial arteriovenous malformations (AVMs) but they are a much more frequent cause of PT than cerebral or neck AVMs. They are usually acquired and may result from recanalized venous sinus thrombosis. Dural AVFs involving the transverse or sigmoid sinus are most frequently implicated in PT ( Fig. 9 ). 20 Direct AVFs between the ICA and the cavernous sinus (carotico-cavernous fistulae) may also cause PT, although pulsatile exophthalmos is a more common presentation. Extracranial AVFs, which usually involve branches of the vertebral artery (but may involve the internal or external carotid arteries), may rarely cause PT. 21 These abnormalities may be detected on CTA/V or post-gadolinium MRI/MRA studies. Findings may be subtle, particularly with in- direct dAVFs. Shin et al. 22 retrospectively re- viewed 54 patients with PT who were evaluated for transverse sinus dural AVFs. CT Arteriovenous fistulae and malformations

products, the lesion enhances avidly and may con- tain flow voids. Meningiomas may diffusely infiltrate the skull base extending into themiddleear and skull base foramina. There may be a ‘‘permeative sclerotic’’ appearance to the bone on CT and there is usually diffuse ‘‘en plaque’’ intracranial enhancement ( Fig. 8 ). Vascular metastases in and around the jugular foramen, from breast, lung, and thyroid primary sites, are a recognized cause of PT. Metastases Transverse CT image of a 68-year-old patient with facial nerve paralysis, sensorineural hearing loss, and PT. There is aggressive bony destruction of the pos- terior left petrous ridge (at the level of the vestibular aqueduct) containing spiculated calcification. The ap- pearance and location are characteristic of an endolym- phatic sac tumour, sporadic in this case, which was confirmed histologically. Figure 7

Figure 9 Lateral projection of an occipital artery an- giogram in a patient with a palpable thrill which was transmitted to the frame of the bed. There is rapid an- terograde drainage of the fistula into the sigmoid sinus. When there is retrograde dural sinus flow and cortical venous drainage, treatment is mandatory to prevent ve- nous hypertension, intracranial haemorrhage, and focal neurological deficits.

Figure 8 Post-gadolinium, T1-weighted, coronal im- age demonstrates enhancing meningioma in the inferior left cerebellopontine angle cistern with enhancement extending into the IAM. There is further extension of the meningioma to fill the left middle ear cavity (other images demonstrated this tissue to be continuous with that in the jugular foramen).

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