Surgical options in the treatment of interhemispheric arachnoid cysts.

BACKGROUND: Arachnoid cysts located within the interhemispheric fissure are a matter of discussion as to the surgical indication and the choice of the most appropriate surgical procedure. In fact, in spite of the large dimensions that they can reach, the clinical manifestations may remain subtle and apparently stable over the years. On the other hand, the larger utilization of prenatal ultrasound investigations has increased the number of lesions detected before they can provoke clinical manifestations. As far as surgery is concerned, two main options are available-an extrathecal shunting procedure or a direct approach to the lesion, with excision of its wall.
METHODS: In this report, we analyze the results obtained in 25 children harboring an interhemispheric arachnoid cyst, surgically treated in the period 1978 to 1994. Mean age at diagnosis was 18.8 months (10 days to 15 years). RESULTS The main clinical manifestations included macrocrania, mild to moderate signs of increased intracranial pressure, cranial bulging, developmental delay, and neurologic signs. In 14 cases, the diagnosis had been obtained prenatally. The cyst was located in one hemicranium in 16 cases, whereas it was on the midline, with bilateral extension, in the remaining 9 cases; in the latter cases, variable degrees of callosal agenesis were also observed. All 25 children were operated on. In 16 of them, the treatment consisted of a craniotomy with wide excision of the cyst lining and marsupialization into the subarachnoid spaces of the midline (and/or into the ventricular system). In 6 children, the surgical procedure was a cystoperitoneal (CP) shunt. The last 3 children of our series underwent craniotomy and cyst excision after having been treated by means of a ventriculoperitoneal shunt. At follow-up examination, 17 children are normal, and the remaining 8 disclose mild to moderate psychomotor retardation.
CONCLUSIONS: Although both craniotomy and CP shunt are associated with good results, the first surgical procedure offers the advantage of avoiding the insertion of a permanent cerebrospinal fluid shunt device and the known complications of this type of procedure.