Understanding Neurology

96Dysphonia refers to impaired vocal cord control,which affects speech. Pathology affecting anyindividual part of this extensive system can result inspecific language or speech impairment. The nature ofthe language deficit varies depending on the site ofpathology. Thus clinical examination can help theclinician to localize what level in the neuraxis isresponsible for the impairment.DISORDERS OF LANGUAGEClassification of aphasiasGiven the understanding of the systems involved inlanguage, it is possible to address how selective lesionsto the language and speech regions result in specificaphasia syndromes. The prime factors to be assessed indetermining the type of aphasias are: fluency,repetition, comprehension, and naming (89).Fluent speech is of normal rate and normal phraselength. Damage to anterior language areas results innonfluent (or expressive) aphasia, in which speech isslow, and said to resemble ‘telegraphic’ communication.Fluency is impaired in Broca’s aphasia, but isspared in Wernicke’s aphasia.Impaired repetition indicates pathology in theperisylvian language areas. An isolated impairmentof repetition is called conduction aphasia, whileselective sparing of repetition occurs in thetranscortical aphasias.Comprehension is impaired in Wernicke’saphasia, and relatively spared in Broca’saphasia.While naming is impaired in all the aphasias,the nature of the naming defect can provide clues asto the type of aphasia, e.g. phonemic paraphasias inBroca’s aphasia.Neuroanatomy of the aphasiasWernicke’s aphasiaLesions to Wernicke’s area produce problems withdecoding of spoken and written language (fluentdysphasia). Here, speech is fluent and there is littleeffort in speaking. Paraphasias (i.e. word errors)occur. These may be semantic paraphasias (e.g.APPLE for ORANGE), or new words (neologisms)may occur in the acute stage. The disorder issometimes described as jargon aphasia (or a wordsalad). Syntax (correct use of grammar andnonsubstantive words) is relatively preserved.Auditory comprehension is always impaired andrepetition is impaired. For instance: ‘We redo, er, theplace, em, near the nettek, thing with wheels’, insteadof ‘We went to the seaside by car’.Transcortical sensory aphasiaTranscortical sensory aphasia is identical toWernicke’s aphasia, except repetition is preserved.The pathology usually involves cortical or deep whitematter damage at the periphery of the perisylvianlanguage areas.89FluencyComprehensionRepetitionWernicke’sImpairedReducedTranscortical sensoryFluentNon-fluentPreservedImpairedNormalReducedNormalConductionAnomicGlobalPreservedReducedBroca’sNormalTranscortical motor89 Diagram to show the classification tree of aphasias.