J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.52.10.1162 on 1 October 1989. Downloaded from Journal ofNeurology, Neurosurgery, and Psychiatry 1989;52:1162-1169 Dichotic listening and manual performance in relation to magnetic resonance imaging after closed head injury HARVEY S LEVIN,* WALTER M HIGH, JR,* DAVID H WILLIAMS,* HOWARD M EISENBERG,* EUGENIO G AMPARO,t FAUSTINO C GUINTO, JR,t JEFF EWERTt From the Division ofNeurosurgery* and the Department ofRadiology,t The University of Texas Medical Branch, Galveston and Department ofPsychology,: University ofHouston, Texas, USA SUMMARY In order to investigate post-traumatic hemispheric disconnection effects, dichotic listening and intermanual tasks were administered to 69 patients who had sustained a closed head injury of varying severity. The manual tasks consisted of naming objects palpated in either hand, transfer ofpostures from one hand to the other and writing. Consistent with predictions, the degree of ear asymmetry in dichotic listening performance was directly related to the severity ofthe head injury as reflected by the degree of impaired consciousness. Depth and localisation of parenchymal lesionguest. Protected by copyright. characterised by magnetic resonance imaging were also related to the degree of ear asymmetry. Parenchymal lesions situated in sites which could potentially interfere with callosal auditory or geniculocortical pathways produced a greater disparity in response to left versus right ear inputs as compared with parenchymal lesions in areas such as the frontal lobes which are purportedly unrelated to asymmetries in dichotic listening performance. The results provide further evidence for the effects of multifocal brain lesions involving the white matter on tasks which require intra and/or interhemispheric integration. Strich' first published microscopic findings of diffuse palpated by the left hand."'0 Utilising the dichotic axonal injury (DAI) which she attributed to mechan- listening technique, Alexander and Warren" recently ical disruption (that is, shearing, tearing) of nerve reported a survivor of severe CHI who exhibited an fibres at the moment of impact in severe closed head exaggerated right ear advantage (that is, left ear injury (CHI). Focal haemorrhages involving the cor- suppression), a finding which the investigators pus callosum, the dorsolateral quadrant(s) of the attributed to a haemorrhagic lesion in the callosal rostral brainstem and the white matter ofthe superior auditory pathways. Although neuropathologic find- cerebellar peduncle are frequent pathological findings ings by Oppenheimer'2 indicated the presence of DAI in DA`.'-5 Degeneration of the cerebral white matter, and corpus callosum lesions in two patients who which presumably occurs over periods ofup to several sustained relatively mild head injuries and died from http://jnnp.bmj.com/ months, has been implicated in lateral ventricular other causes, more recent neuropathological and enlargement' 256 and long tract signs such as ataxia.7 antemortem magnetic resonance imaging (MRI) Consistent with disruption of intra and interhemis- studies'3 4 have shown that deep white matter lesions pheric white matter connections in DAI, clinical are generally restricted to CHI which produces coma. reports have documented neurobehavioural distur- This positive relationship between impairment of bances such as ideomotor apraxia using the left hand, consciousness and depth of lesion is also compatible alexia without agraphia and tactile anomia for objects with previous experimental work in nonhuman primates by Ommaya and Gennarelli.'5 In view of on September 30, 2021 by Correspondence to: Harvey S Levin, PhD, Division of Neurosurgery previous studies'S implicating nontraumatic brain D-73, The University of Texas Medical Branch, Galveston, Texas lesions in the auditory interhemispheric connections, 77550, USA. geniculocortical pathways and temporal cortex in Received 11 October 1988 and in revised form 10 March 1989. abnormal dichotic listening, it is plausible that the Accepted 21 March 1989 localisation ofbrain lesion is related to ear asymmetry 1162 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.52.10.1162 on 1 October 1989. Downloaded from Dichotic listening, manualperformance and MRI in closed head injury 1163 in performance by head injured patients. Conse- to dictation.23 They were asked to identify hidden common quently, this study evaluated the relationship between household objects by palpating them with either hand23 and and localisation of tested for matching postures with the ipsilateral or contra- severity of acute CHI, depth lateral hand, in the absence of visual cues." ' The examiner intracranial lesion defined by MRI, and neuro- placed the patient's hand and fingers (hidden from the behavioural evidence of hemispheric disconnection. patient's view) in one of 10 positions followed immediately by returning the hand to the resting position. The patient was Methods asked to then duplicate the posture using either the same hand or the contralateral hand. Patients Selection criteria for this prospective study included Magnetic Resonance Imaging hospitalisation for CHI of varying severity, resolution of post-traumatic amnesia, a negative history of antecedent The MRI scans were obtained in Houston and Galveston neuropsychiatric disorder (including previous hospitalisa- within one week of the neurobehavioural testing. MRI was tion for head injury or chronic substance abuse) and an age performed in Houston on a 0 35 Tesla magnet with a proton range of 15 to 60 years. This report is confined to right resonant frequency of 15 MHz, with imaging in the transaxial handed patients to simplify analysis of hemispheric asym- and coronal planes using the spin-echo technique, slice metries which are known to differ in those that are left thickness 7 mm and slice interval 3 mm. The repetition time handed. We studied 69 right-handed patients with a mean age (TR) was 2000 s and echo times (TE) were 38 and 56 ms. of 25-6 years (SD = 9 9) and a mean education of 11-8 years MRI was performed in Galveston on the Teslacon System (SD = 2 4) who sustained CHI of varying severity (table 1). using a 0-6 Tesla magnet with a proton resonant frequency of As shown in this table, the interval from injury to the 25-4 MHz. Images were obtained in contiguous 8 mm slices examination tended to be longer in more severely injured in the transaxial and coronal planes using two spin echo (SE) patients. All patients were hospitalised in Galveston (The sequences primarily: (a) repetition time (TR) was 500 ms and University of Texas Medical Branch) or Houston (Medical echo time (TE) was 32 ms and (b) TR = 2000 ms and TE = Center Del Oro) at the time of examination or had been 60 ms, 120 ms. Two radiologists interpreted the neuro- guest. Protected by copyright. discharged within three months of the study. Following the imaging findings independently of other data on the severity guidelines ofa recent three centre study,2' a minor head injury ofthe head injury and hemispheric disconnection symptoms. was defined as loss of consciousness for no longer than 15 Radiologists also coded the MRI results on research forms minutes, a Glasgow Coma Scale (GCS)22 score of 13 to 15 on which were compatible with computer entry. Intracranial admission and for the duration ofthe hospital stay, a normal abnormalities on MRI were coded as lesions provided that neurological examination, and normal findings on the first they were present on both the first and second echoes of computed tomography (CT) scan (if performed). Patients T2-weighted images. with GCS scores in the 13 to 15 range who had a positive CT scan (that is, evidence of a high density lesion, brain swelling) Results and/or intracranial surgical procedures (for example, repair of depressed fracture) were grouped with the moderate to Dichotic listening severe injuries (table 1). Intracranial lesions visualised by Effects ofseverity ofhead injury. Figure 1 depicts a box MRI, which were undetected by CT, were not considered in the classification of severity of injury. plot showing the median and interquartile range of the Thirteen right handed controls, mean age 24-0 years (SD laterality index for the control group and the patients = 7-1), mean education 121 years (SD = 17), were also who are divided into subgroups according to the tested. All patients and controls passed an auditory screening severity of their head injury, and the depth and test given to each ear separately and to both ears simulta- localisation of the brain lesion. Laterality indices for neously. patients and controls (see table 1) on the dichotic listening task were ranked and an analysis of variance Procedures was performed on the ranks to test the presence of a http://jnnp.bmj.com/ Dichotic listening difference in asymmetry of performance across the The dichotic tape consisted of six consonant vowel (C-V) control (n = 13), minor CHI (n = 7), and moderate to nonsense syllables (ta, pa, ka, ga, ba, da). Pairs of C-V severe CHI (n = 62) groups. As reflected by the syllables were presented simultaneously at equal volumes to greater laterality index for moderate to severe injuries the right and left ears via earphones. The patient was shown in fig 1, the presence of a group effect for instructed to call out the syllables presented on each of 60 asymmetry in ear scores was confirmed (F = 3-12, p < trials. Earphones were reversed to the opposite ears after the 005). Post hoc comparisons