rournal ofNeurology, Neurosurgery, and Psychiatry 1995;59:293-298 293 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.59.3.293 on 1 September 1995. Downloaded from Arachnoid cysts of the left temporal fossa: impaired preoperative cognition and postoperative improvement Knut Wester, Kenneth Hugdahl Abstract possible toxic products. The mechanisms Thirteen adult patients were operated on underlying neurological deficit in such indo- for symptomatic arachnoid cysts in the lent lesions as arachnoid cysts are far from left temporal fossa; seven with an inter- clear. The intracranial pressure is seldom nal shunt procedure during local anaes- raised enough for reduced tissue perfusion to thesia, and five with a craniotomy with be the mechanism underlying loss of function. fenestration of the cyst to the basal cis- Because clinical improvement may occur after terns. In one patient, an initial internal decompression, it would seem likely that the shunt was transformed to a cystoperi- neurological deficit is related to processes toneal shunt. After surgery, all patients which, although impairing neuronal function, experienced relief of symptoms. do not necessarily result in cell death. Reduction of cyst volume occurred in 11 Arachnoid cysts are thought to be due to a patients. The patients were tested for maldevelopment of the cerebral meninges."2 brain asymmetries related to language This may be present at birth or develop soon and verbal memory before and after after.34 After an initial growth in early life, operation, with a dichotic listening tech- most cysts are thought to remain stable over nique with simultaneous presentation of many years,5 having reached a permanent size different auditory stimuli to the two ears. which may well be substantial. Very few cysts In the preoperative memory test, the have been reported to disappear sponta- patients showed impaired total recall neously.6-'0 Moreover, some seem to continue compared with healthy control subjects, to grow in adult life; although slowly." and recall from the right ear was signifi- The symptoms associated with arachnoid cantly impaired. The patients also per- cysts vary according to the site of the lesion formed poorly in a forced attention task and the neural structures surrounding them. consisting of dichotic presentations of In adults, subjective complaints such as consonant-vowel syllables. In addition to headache and dizziness are common. Major clinical improvement, the surgical proce- neurological symptoms such as motor or sen- dures led to improvements in both sory deficits, epilepsy, or language problems dichotic perception and memory. Overall may also occur, although they are often slight memory performance was enhanced, and tend to develop late in life. The lack of mainly because of improved recall from dramatic symptoms, even in patients with http://jnnp.bmj.com/ the right ear. This normalisation of large arachnoid cysts, probably reflects the memory function was found as early as brain's ability to compensate for the presence four hours after the operation. The of a slowly growing or stable expansion. results indicate that arachnoid cysts in If arachnoid cysts cause disabling symp- the left temporal fossa may impair cogni- toms such as a paresis, dysphasia, epilepsy, or tive function, that neuropsychological severe headache, or they are complicated by a tests are necessary to disclose these subdural haematoma, there is a clear indica- impairments, and that cognitive tion for surgery. On the other hand, if the on September 27, 2021 by guest. Protected copyright. Department of improvement occurs after surgery. symptoms are less dramatic, some authors Neurosurgery, favour conservative treatment.'2-'7 The rela- University of Bergen, (3 Neurol Neurosurg Psychiatry 1995;59:293-298) tive paucity of symptoms despite massive dis- School ofMedicine, Haukeland Hospital, placement of brain tissue is taken to indicate N-5021, Bergen, satisfactory cerebral compensation.'8 Norway Key words: arachnoid cysts; language; memory. Moreover, some earlier series reported a sig- Knut Wester nificant mortality and morbidity after surgery Department of for these Biological and "uncomplicated" cases, and this has Medical Psychology, Lesions occupying intracranial space, such as also prompted caution.'3 19-22 University of Bergen, haematomas, tumours, or cysts may impair In common with any other intracranial Arstadveien 21, N- brain function. The underlying mechanisms expansive lesion, arachnoid cysts have the 5011,Bergen, Norway Kenneth Hugdahl for this disturbance in the case of rapidly potential to impaire cognitive function. Such Correspondence to: Dr expanding haematomas are well understood, impairments may well contribute to the Knut Wester, Department and may be related to changes in general or patient's incapacity, but are not easily shown of Neurosurgery, Haukeland Hospital, N-5021, Bergen, local tissue perfusion. The reduced cerebral by a clinical neurological examination. To Norway. perfusion may be due to raised intracranial date, subtle cognitive impairments associated Received 3 January 1995 pressure, complicated by the presence of with intracranial expansions have received and in revised form 3 April 1995 oedema, itself a mass lesion, changes in much less attention than the more dramatic Accepted 19 April 1995 cerebrovascular reactivity, or the diffusion of and easily recognisable overt neurological 294 Wester, Hugdahl J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.59.3.293 on 1 September 1995. Downloaded from symptoms and findings. Indeed, there are few one patient (4) with a recent history of head reports dealing with cognitive functions in trauma, a subchronic subdural effusion/ patients with arachnoid cysts. Lang et al3 haematoma overlying the cyst was drained found a reduced ability to learn and memorise separately before the preoperative dichotic lis- hemisphere specific material in patients with tening tests and the shunt operation that middle fossa cysts, whereas other reports have eventually drained the cyst. failed to show cognitive impairments in such patients.'5 24 CONTROL GROUPS If cognitive deficits could be shown in Seven patients with arachnoid cysts of the patients with otherwise "silent" cysts, and if right temporal fossa served as a control group cyst surgery improves these functions, the for the preoperative scores. As only three of indications for surgery may be expanded con- these patients were operated on statistical siderably, and the decision to operate would analyses of the effects of decompressive be taken on a broader basis. surgery in patients with right sided cysts could Nearly half of the arachnoid cysts occur in not be performed. the middle cranial fossa,' with a pronounced Healthy subjects (age <50 years) also preference for the left side.25 Most cysts there- served as normal controls in both the dichotic fore affect the speech dominant hemisphere. memory (n = 32), and the dichotic listening For this reason, two tests were chosen for the (n = 52) tests. present study, based on the dichotic listening technique.26 These tests are sensitive to differ- DICHOTIC LISTENING STIMULUS MATERIALS ences in hemispheric functions and in particu- AND TEST PROCEDURES lar probe left hemispheric verbal functions. We used a modified version of the dichotic Dichotic listening procedures have previously memory test described by Christianson et al.30 proved sensitive in reflecting changes in pro- Three different series of 10 nouns were pre- cessing of verbal stimuli produced by discrete sented two seconds apart to the right or the electrical stimulation of the ventrolateral left ear, with the same nouns played simulta- thalamus27 28 and in recovery of language func- neously backwards to the other ear. The tions after a stroke.29 Moreover, a memory patients were asked to recall all items remem- version of the dichotic listening test was used bered for 30 seconds after each series of 10 by Christianson et aP' when investigating words. The results were averaged over the hemispheric specific memory impairments in three series, the maximum score for each ear two cases of localised head trauma. thus being 10. To control for possible learning effects due to repeated presentations of the dichotic memory test, three parallel versions Patients and methods of the test were used. There might, however, PATIENTS still be some learning of the test situation Thirteen consecutive patients (11 men, two itself. To control for this possibility, seven women) were included in the study as the patients with left sided cysts and three with a experimental group. To keep the material as similar cyst on the right side were tested (pre- homogenous as possible, only patients with operatively) more than once. cysts in the left temporal fossa were included. Preoperatively, each patient was tested at Another inclusion criterion was clinical least once. Only the score from the first pre- http://jnnp.bmj.com/ improvement after surgery (experienced by all operative test was used as the preoperative the patients). Handedness was defined with score in the statistical analyses. For seven of the help of a Norwegian translation of the the patients operated on under local anaesthe- questionnaire developed by Raczkowski et al." sia, the immediate postoperative condition The patient had to indicate 13 of the 15 items was so good that it allowed systematic collec- performed with the right hand to be classified tion of data two or three times during the first as right handed. Two of the patients (1 and 7) postoperative week. The first of these postop- indicated preference for the left hand; the erative tests took place four hours after the on September 27, 2021 by guest. Protected copyright. others were classified as right handers. operation, except in patient 1 who was tested Hearing acuity was determined by a Tegner after 24 hours. The immediate postoperative screening audiometer. All patients had normal condition did not allow a similar systematic hearing, and patients with an imbalance in testing during the first postoperative week in hearing between the ears of more than 5 dB the patients operated on with a full cran- were not included in the study.