A 20-year-old right-handed male with a large left temporal arachnoid cyst, discovered incidentally by CT following a kick to the head with brief loss of consciousness, is reported from the University of Texas Medical Branch, Galvestan, TX. MRI revealed a mass effect with midline shift and left temporal lobe hypoplasia. Severe headaches had increased in frequency for one year after the head trauma. Early history and developmental milestones were normal, but learning disabilities and behavior disorder lead to school drop-out at 11th grade. Pre-surgery psychological testing revealed a borderline verbal IQ of 76 and average performance IQ. of 90, with clinical discrepancy in verbal (left hemisphere) and visual-perceptual/constructional (right hemisphere) skills. Bilateral deficits were observed on a test of speed of motor coordination. School records were comparable to the post-trauma test scores. Craniotomy with cyst fenestration and cystoperitoneal shunt resulted in minimal change in size of cyst. Psychological testing at 1 year postsurgery showed no change in language function but significant cognitive improvements in verbal learning, memory, visual-perception/constructional skills, and psychomotor speed, with a 27-point increase in Performance IQ to 117. Reliance on anatomical decompression of the arachnoid cyst may underestimate the efficacy of surgical intervention. 
COMMENT. Surgical intervention in certain cases of left temporal arachnoid cyst can result in improved cognitive function despite only marginal reduction in size of the cyst. In addition to refractory seizures and headaches, cognitive measures should be used as a functional index of surgical intervention and outcome.
Neurosurgeons in general are reluctant to operate on arachnoid cysts, except in cases complicated by mass effect with seizures and headaches. The report of a Temporal Lobe Arachnoid Cyst/ADHD syndrome, described recently in children with coincidental learning and language disabilities, has emphasized the importance of tests for associated attention deficits and learning disorders in children with arachnoid cysts located in the temporal fossa . PET studies have sometimes demonstrated hypometabolism in cortical areas adjacent to a cyst, and cystoperitoneal shunt can result in improved metabolism and language function. A neurobiologie basis for ADHD, suggested by the TLAC/ADHD syndrome, may prove amenable to surgery in cases of arachnoid cyst complicated by symptoms of a mass effect.