The clinical manifestations and associated brain anomalies of intracranial arachnoid cysts are reported in 30 children treated at the National Taiwan University Hospital, Taipei. Onset of symptoms ranged from 1 day to 14 years (mean, 4 years, 7 months), and age at diagnosis was 10 days to 16 years (mean, 6 years, 2 months). The majority of cysts were located in the middle fossa, usually unilateral (17 cases); 7 were in the posterior fossa. Presenting clinical symptoms included seizures in 11 cases (37%), headache in 6 (20%), and macrocephaly (2 cases). EEG showed focal temporal or central epileptiform discharges in 13 of 17 patients. In patients with intractable seizures, surgery resulted in only partial reduction in cyst size and seizure frequency. Progressive hydrocephalus and increased intracranial pressure occurred in 2 patients and were relieved by ventriculo-peritoneal shunt. Associated anomalies included brain tumor, nevocellular nevi, achondroplasia, microphthalmia, intracystic hemorrhage, corpus callosum dysgenesis, and heterotopia. 
COMMENT. Intracranial arachnoid cysts (AC) may be asymptomatic and are recognized incidentally by CT or MRI for head trauma or at autopsy. Some are identified by neuroimaging performed because of headache, seizures, ataxia, or macrocephaly. The pathophysiology is a congenital malformation of the leptomeninges. The temporal lobe or middle cranial fossa is the most common location. The conservative approach to treatment, usually favored by neurosurgeons, is based on lack of sustained benefit and a 30% risk of cyst recurrence after surgery.
In addition to headaches and seizures, the most common presenting symptoms of AC, attention deficit hyperactivity disorder has been associated with temporal lobe AC, the TAC/ADD syndrome . A causal association was considered plausible based on the coincidental learning and language disabilities that might be explained by temporal lobe and sylvian region pathology in the the initial 3 cases reported. Since this publication, I have diagnosed one further case and colleagues have provided me with case reports of 3 examples of the TAC/ADD syndrome. The EEG was normal in 2 and at follow-up in one other whose initial record had shown focal temporal slow and sharp waves. Cases of AC involving the temporal lobe warrant psychological testing for associated ADHD and learning disorders.