Cerebellopontine Angle Arachnoid Cyst in an Adult Patient: Diagnosis and Management

The incidence of arachnoid cysts is 1% of all intracranial lesions. The cerebellopontine angle (CPA) is a rare location for arachnoid cysts, and fewer than 35 cases of arachnoid cysts occurring in the CPA have been reported in the literature. We discuss the diagnosis, radiographic imaging, and management of CPA arachnoid cysts. Arachnoid cysts often present with only subtle signs or symptoms, such as headache or ataxia. Our case involves a middle-aged, female patient, who presented with unilateral tinnitus, unsteadiness, and headaches associated with nausea and vomiting. On clinical examination there were no cerebellar signs or cranial neuropathy; she did, however, suffer from a unilateral mild to severe hearing loss. Recent advances in MRI (magnetic resonance imaging) scan techniques have led to more frequent diagnosis of CPA arachnoid cysts and with a higher degree of certainty. These lesions have a characteristic location in the posterior-inferior aspect of the CPA below the facial and vestibulocochlear nerves. Although CPA arachnoid cysts represent a small number of total arachnoid cysts, the CPA is the second most common location for arachnoid cysts to occur. The optimal surgical management of arachnoid cysts remains controversial. Most surgeons advocate that the definitive treatment for arachnoid cysts is a retrosigmoid suboccipital craniotomy and microsurgical resection and fenestration of the cyst walls. However, these cysts often do not show any change in size on repeated MRI scan and the patients' symptoms do not progress over a long period of follow-up. These clinical and radiological findings would support a conservative management approach to the majority of the arachnoid cysts.