BACKGROUND: The decision making process for patients with Sylvian fissure 
arachnoid cysts still represents a challenge for the neurosurgeon. A high 
percentage of patients are indeed asymptomatic, despite neuroimaging signs of 
apparently increased intracranial pressure (ICP). The present study was 
conducted to evaluate the usefulness of prolonged ICP recording in the 
preoperative work-up.
METHODS: Eleven children (10 M/1 F) harboring temporal arachnoid cysts were 
investigated (mean age: 5.9 years). According to Galassi classification they 
were subdivided in three groups. Group I was made up of three patients with Type 
I cysts; Group II comprised six children with Type II cysts; Group III consisted 
of two children with Type III cysts. An extensible silicone microprocessor 
(Codman), developed for continuous ICP recording, was implanted 
intraparenchymally, adjacent to the major extension of the cyst. The collected 
information was cable unloaded to a PC and stored. All the patients underwent a 
minimum of 48 hours to a maximum of 72 hours of ICP continuous check. In resting 
conditions, 10 mm Hg was arbitrarily chosen as the upper normal limit of ICP, 
and the patients were classified according to the percentile distribution of 
their ICP daily and nightly pressure values.
RESULTS: ICP recordings were in the normal range in all the three children with 
Type I cysts (49-86%< 10 mm Hg during the entire recording), despite the fact 
that two of them were apparently symptomatic. Three of the six children with a 
Type II temporal cyst had elevated ICP values (69-99%> 10 mm Hg), even though 
they had an incidental (1 case) or prenatal (2 cases) diagnosis. The remaining 
three patients had normal ICP values for more than 70% of the recording time 
period. The two patients with type III temporal arachnoid cysts had almost 
constantly abnormal ICP values (95-99%> 10 mm Hg). Five patients were operated; 
in four of them the surgical indication was based on ICP recordings (two of the 
three children with a Type II cyst and increased ICP and the two patients with a 
Type III cyst). The last child, harboring a Type I cyst, was operated upon 
parents' request, as a preventive measure. At a mean follow-up of 9.3 months all 
the patients operated on are in excellent clinical condition; one of them (Type 
II cyst) initially undergoing a craniotomy and cystic membrane excision required 
a subduro-peritoneal shunt implant 3 months after surgery for a symptomatic 
subdural hygroma on the side of the cyst. Postoperative computed tomography 
showed signs of brain expansion in the two patients operated on for a Type III 
cyst, and in the patient operated on for a Type I cyst.
CONCLUSIONS: With the limit of the relatively small series presented here, 
prolonged ICP recording appeared to be an important preoperative tool to rule 
out the necessity of operating on children with Type I cysts. Furthermore, the 
study confirmed that an increase of the ICP is almost constantly present in 
children with Type III cysts. In cases of Type II lesions, the study results 
were less discriminating, though the ICP monitoring contributed in identifying 
those patients in whom surgery was indicated despite the absence of symptoms.