Functional assessment of intracranial arachnoid cysts with TC99 m-HMPAO SPECT: a preliminary report

Abstract

Many arachnoid cysts (AC) are detected incidentally in asymptomatic patients. Current neuroimaging methods provide only morphological details of the cysts, but they do not give information about cerebral function. While surgery is indicated in symptomatic patients, the management of asymptomatic individuals, who present with large cysts, is controversial. To ascertain the value of cerebral 99 mTc-HMPAO single photon emission computed tomography (SPECT) for detecting brain dysfunction in cases of intracranial ACs, aimed at allocating the patients for surgical or for conservative treatment. We studied prospectively 11 patients diagnosed with sylvian fissure ACs. The subjects underwent neurological examination, EEG, neuroimaging studies, neuropsychological testing, and cerebral perfusion studies with 99 mTc-HMPAO SPECT. The patients' ages ranged from 2 to 42 years (median 16 years). The study group consisted of ten symptomatic patients with ACs and one patient with an incidental cyst. Seven patients showed diminished regional cerebral blood flow (rCBF) in their initial cerebral SPECT. Four individuals underwent surgery. Seven patients showed normalization of rCBF after surgical or conservative treatment. Cerebral SPECT demonstrated impaired brain perfusion in 70% of symptomatic patients. The zone of decreased rCBF corresponded well with clinical symptoms and with neuroimaging findings. Patients exhibiting normal rCBF in SPECT studies remained or became asymptomatic during the follow-up time. Cerebral SPECT constitutes a valuable adjunct tool for correlating regional function with brain anatomy, and may be of help to allocate patients with ACs for surgical treatment or clinical observation. Further research on this field is warranted.