ing ophthalmoplegia, initially misdiagnosed as suffering from migraine, cluster headaches, To- losa-Hunt syndrome or intracranial aneurysms, have been described as well (Hawke et al. 1989; Brazis et al. 1994; Komorsky 1988).

6.1.2

Cranial Nerve Deficits and Ophthalmoplegia

Unilateral ophthalmoplegia can be seen in ca. 50% of the patients with DCSFs (Miyachi et al. 1993) and often represents the first objective symptom. It usually becomes manifest after weeks or months following development of a fistula. The elevated intraorbital venous pressure leads to a progressive swelling of the ocular muscles and to a reduced contractility and limited motility of the eye bulb. On the other hand, dilated vessels and vascular steal phenomena result in mechanical and ischemic oculomotor nerve damage.

Due to their course through the CS, the sixth CN is most frequently (46%–85%), the third CN less frequently (36%) and usually in cases with posterior

drainage, and the fourth CN (11%) is rarely involved (Kupersmith et al. 1986, 1988).

In cases of anterior drainage, the ophthalmoplegia is often accompanied by other orbital symptoms such as exophthalmos and chemosis. In contrast, fistulas with posterior drainage via the IPS may be the cause for isolated ophthalmoplegia and should be included in the differential diagnoses of intracranial neoplasms, cavernous aneurysms and meningitis (Acierno et al. 1995). Although diplopia in these patients is usually reversible, it requires intensive neuro-ophthalmological care and early intervention. In some cases of longstanding AV shunting into the CS, diplopia may become permanent.

6.2

Orbital Symptoms

Several authors postulate anterior drainage or disturbance of the anterior venous outflow from the