Clinical characteristics of arteriovenous malformations in the cerebellopontine angle cistern.

OBJECTIVE Arteriovenous malformations (AVMs) in the cerebellopontine angle cistern (CPAC) are specific lesions that can cause neurovascular compression syndromes as well as intracranial hemorrhage. Although case reports describing the CPAC AVMs, especially those presenting with trigeminal neuralgia (TN), have been accumulating by degrees, the pathophysiology of CPAC AVMs remains obscure. The authors' purpose in the present study was to evaluate the clinical and radiographic features of CPAC AVMs as well as the treatment options. METHODS This study defined a CPAC AVM as a small AVM predominantly located in the CPAC with minimal extension into the pial surface of the brainstem and closely associated with cranial nerves. All patients with CPAC AVMs treated in the authors' affiliated hospitals over a 16-year period were retrospectively identified. Clinical charts, imaging studies, and treatment options were evaluated. RESULTS Ten patients (6 men and 4 women), ranging in age from 56 to 77 years (mean 65.6 years), were diagnosed with CPAC AVMs according to the authors' definition. Six patients presented with hemorrhage, 3 with TN, and the remaining patient developed a hemorrhage subsequent to TN. Seven AVMs were associated with the trigeminal nerve (Group V), and 3 with the facial-vestibulocochlear nerve complex (Group VII-VIII). All patients in Group VII-VIII presented with the hemorrhage instead of hemifacial spasm. Regarding angioarchitecture, the intrinsic pontine arteries provided the blood supply for all CPAC AVMs in Group V. In addition, 5 of 7 AVMs with hemorrhagic episodes accompanied flow-related aneurysms, although no aneurysm was detected in patients with TN alone. With respect to treatment, all patients with hemorrhagic presentation underwent Gamma Knife surgery (GKS), resulting in favorable outcomes except for 1 patient who experienced rebleeding after GKS, which was caused by the repeated rupture of a feeder aneurysm. The AVMs causing TN were managed with surgery, GKS, or a combination, according to the nidus-nerve relationship. All patients eventually obtained pain relief. CONCLUSIONS Clinical symptoms caused by CPAC AVMs occur at an older age compared with AVMs in other locations; CPAC AVMs also have distinctive angioarchitectures according to their location in the CPAC. Although GKS is likely to be an effective treatment option for the CPAC AVMs with hemorrhagic presentations, it seems ideal to obliterate the flow-related aneurysms before performing GKS, although this is frequently challenging. For CPAC AVMs with TN, it is important to evaluate the nidus-nerve relationship before treatment, and GKS is especially useful for patients who do not require urgent pain relief.