Outcome in Landau-Kleffner syndrome (LKS) is generally poor. Fewer than one-third of the original LKS patients ultimately had normal language ability, one-third had mild to moderately impaired language ability, and one-third had severely impaired language ability.127
Dugas et al.40 recently reviewed the literature on the follow-up of 55 LKS patients (at least 14 years of age at the time of follow-up and followed for at least 7 years) with and without continuous spikes and waves during slow sleep (CSWS) and found a similar distribution, with perhaps a slightly smaller percentage of patients experiencing a good outcome.
Another follow-up study conducted on a group of 12 patients (75% of whom had exhibited some language disturbance prior to acquired epileptic aphasia) followed for 2 to 15 years (mean, 8 years) found that only 3 achieved normal language ability, even though the EEG normalized in 9 patients.102
During very long-term follow-up (20–30 years), all four patients studied showed marked recovery in language without any intellectual handicap but with some disability in spoken language, auditory verbal perception, and a discrepancy between Wechsler Verbal and Performance IQ scores.13
Clinical or EEG features may affect outcome. Younger patients fare less well than do older patients,128 and those with CSWS may have a poorer outcome. In only 2 (18.2%) of 11 patients with CSWS was language recovery complete after a mean follow-up of 9 years.100 (Of these 11 patients, 7 (63.6%) were mentally retarded.)
"Crowding" (recovery of language at the expense of ordinarily right hemisphere–mediated functions) may be seen in those with good language outcome.87,127,129 This pattern suggests that reorganization with transfer of language to the right hemisphere underlies recovery. This subgroup with seemingly focal pathology may be distinguishable from other patients with LKS and its variants.
Case studies provide important information about particular linguistic features and linguistic recovery patterns. The features of verbal auditory agnosia have been examined in some detail, particularly in longitudinal studies. For example, a case study describes a 27-year-old woman with chronic auditory agnosia after LKS, which was diagnosed at age 4.5 years. Manually coded (signed) English allowed for good communication. Comprehension and production of spoken language remained severely compromised. Disruptions in auditory processing were observed in tests of pitch and duration, suggesting that her disorder was not specific to language. Linguistic analysis of signed, spoken, and written English indicated that her language system is intact but compromised because of impoverished input during the critical period for acquisition of spoken phonology. Specifically, although her sign language phonology is intact, her spoken language phonology is markedly impaired. Deprivation of auditory input during a period critical for the development of a phonological grammar and auditory-verbal short-term memory may limit lexical and syntactic development.97
Another patient followed from age 6 to 15 years had a fluctuating clinical course with improvement and worsening of aphasia and epilepsy. At the end of the follow-up period, the boy was seizure-free and had moderately disturbed language production and comprehension. The results of linguistic evaluation suggested that the aphasic disturbance was related to a deficiency in phonologic decoding, which leads to phonologic, morphosyntactic, and lexical disturbances. A temporal relationship between the electroclinical picture and the aphasia was observed: persisting improvement in linguistic performance took place only after disappearance of the seizures and the epileptiform abnormalities during sleep.104 In addition, intraoperative evoked potential recording (during MST) documented the ability to distinguish between different consonant-vowel syllables, despite verbal-auditory agnosia.12
Reviewed and revised May 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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