Unilateral hemispheric lesions disrupt parallel processing within the contralateral intact hemisphere: an auditory fMRI study

Evidence from activation studies suggests that sound recognition and localization are processed in two distinct cortical networks that are each present in both hemispheres. Sound recognition and/or localization may, however, be disrupted by purely unilateral damage, suggesting that processing within one hemisphere may not be sufficient or may be disturbed by the contralateral lesion. Sound recognition and localization were investigated psychophysically and using fMRI in patients with unilateral right hemisphere lesions. Two patients had a combined deficit in sound recognition and sound localization, two a selective deficit in sound localization, one a selective deficit in sound recognition, and two normal performance in both tasks. The overall level of activation in the intact left hemisphere of the patients was smaller than in normal control subjects, irrespective of whether the patient's performance in the psychophysical tasks was impaired. Despite this overall decrease in activation strength, patients with normal performance still exhibited activation patterns similar to those of the control subjects in the recognition and localization tasks, indicating that the specialized brain networks subserving sound recognition and sound localization in normal subjects were also activated in the patients with normal performance, albeit to an altogether lesser degree. In patients with deficient performance, on the other hand, the activation patterns during the sound recognition and localization tasks were severely reduced, comprising fewer and partly atypical activation foci compared to the normal subjects. This indicates that impaired psychophysical performance correlates with a breakdown of parallel processing within specialized networks in the contralesional hemisphere.

Moderate hypothermia improves neurobehavioral deficits after an epidural focal mass lesion in rodents

The objective of this study was to evaluate the effects of a moderate, intraischemic hypothermia on the behavorial deficits up to 4 weeks after induction of a focal mass lesion. A focal epidural mass lesion was induced by an epidural balloon. The severity of the trauma was defined by the balloon volume and flattening of electroencephalography. Hypothermia (32 degrees C) was induced as soon as maximum balloon infIation was reached. Ischemia was extended over 30 min. After reperfusion, normothermic (n = 24) and hypothermic animals (n = 25) were monitored for 3 h followed by a rewarming of the cooled animals. Results were compared to sham-operated animals (n = 10). Behavioral deficits were assessed by postural reflex (PR), open field (OF), beam balance (BB), beam walking (BW), and water maze tests (WMT). MRI follow-up and histology was evaluated. Sham-operated rats showed normal test results. Rats with normothermia showed worsening of test performance (PR, p < 0.05; OF, p < 0.05; BB, p < 0.05; BW, p < 0.05; WMT, p < 0.05) compared to controls over the whole observation period. A significantly better behavioral outcome was observed in animals treated with hypothermia which showed no differences from controls 3-4 days after injury (PR, OF, BB, BW, WMT, p > 0.05). Lesion induced mortality was reduced in cooled animals but overall mortality rates were not influenced by this therapeutic measure. Neuronal cell loss in the CA1-CA4 region (p < 0.05) was reduced and the lesion size smaller (21%/p > 0.05) in hypothermic animals. Magnetic resonance imaging revealed that the lesion was more pronounced in the cortical grey matter after normothermia, whereas hypothermic animals showed more subcortical brain lacerations. In conclusion, intraischemic hypothermia significantly improved the behavioral outcome, and decreased lesion-induced mortality and the size of the lesion after an epidural focal mass lesion.

Asymptomatic or minimally symptomatic traumatic epidural haematomas: comparison of the results of surgical and conservative management related to SPECT and neuropsychological tests. Preliminary results

One hundred and thirteen patients with asymptomatic or minimally symptomatic epidural heamatomas treated surgically or conservatively in our department were collected prospectively. Between 3 and 6 months after the head injury a SPECT (single photon emission computed tomography) study for evaluation of the three-dimensional cerebral blood flow distribution and extensive neuropsychological tests were performed in 22 patients. The preliminary results of this prospective study have demonstrated that minimally symptomatic or asymptomatic EDHs cause no pathologic SPECT findings and that neuropsychological impairment and duration of the haematoma do not affect the results of conservative management.

Valproate in the treatment of posttraumatic bipolar disorder in a psychogeriatric patient

The authors present an 83-year-old man who had developed posttraumatic bipolar disorder 22 years earlier. His condition was characterized by recurrent manic and depressive attacks. Valproate was found effective in controlling his symptoms.

Tactile agnosia and tactile aphasia: symptomatological and anatomical differences

Two patients with tactile naming disorders are reported. Case 1 (right hand tactile agnosia due to bilateral cerebral infarction) differentiated tactile qualities of objects normally, but could neither name nor categorize the objects. Case 2 (bilateral tactile aphasia after operation of an epidural left parietal haematoma) had as severe a tactile naming disturbance as Case 1, but could categorize objects normally, demonstrating that tactile recognition was preserved. Case 1 may be the first case of tactile agnosia clearly differentiated from tactile aphasia. CT scans of Case 1 revealed lesions in the left angular gyrus, and in the right parietal, temporal, and occipital lobes. Case 2 had lesions in the left angular gyrus and of posterior callosal radiations. Our findings suggest that tactile agnosia appears when the somatosensory association cortex is disconnected by a subcortical lesion of the angular gyrus from the semantic memory store located in the inferior temporal lobe, while tactile aphasia represents a tactual-verbal disconnection.

[Decrease in the incidence of epidural hematomas surgically treated during coma after a lucid interval. Is this an index of quality of care?]

The level of consciousness prior to surgery has been analyzed in a series of 64 patients suffering epidural hematoma (EDH) who underwent surgery during the period from July 1987 to June 1989. The percentage of cases which underwent surgery in coma after a lucid interval have been compared in different periods of time (1978-80, 1981-82, 1983-84 and July 1987 to June 1989). During the period from July 1987 to June 1989 surgery was performed on: 15 patients (23.5%) in coma from the moment of accident, 8 patients (12.5%) underwent surgery in coma but after a lucid interval and 41 patients (64.1%) were conscious. During the different periods of time the number of patients undergoing surgery in coma after a lucid interval were the following: 1979-80, 9 cases (26.5%); 1981-82, 17 cases (43.6%); 1983-84, 8 cases (20%) and during the last period, 1987-89, 7 cases (15.2%). The difference between the percentage of patients intervened in coma after a lucid interval in the previously referred periods of time was statistically significant (p 0.05).

Two mental calculation systems: a case study of severe acalculia with preserved approximation

We report the case of an aphasic and acalculic patient with selective preservation of approximation abilities. The patient's deficit was so severe that he judged 2 + 2 = 5 to be correct, illustrating a radical impairment in exact calculation. However, he easily rejected grossly false additions such as 2 + 2 = 9, therefore demonstrating a preserved knowledge of the approximate result. The dissociation between impaired exact processing and preserved approximation was identified in several numerical tasks: solving and verifying arithmetical operations, number reading, short-term memory, number comparison, parity judgement, and number knowledge. We suggest the existence of two distinct number-processing routes in the normal subject. One route permits exact number representation, memory and calculation using symbolic notation. The other route allows for approximate computations using an analog representation of quantities.

Epidural hematoma: an unusual presentation

The authors present a patient with a traumatic epidural hematoma who complained only of headache and presented to the emergency department 48 hours after a fall. Mental status and neurological examination were normal. This delayed presentation is more commonly seen when a subdural hematoma is present but may result from epidural bleeding. Delayed formation of a traumatic epidural hematoma may occur when the following are present: elevated intracranial pressure, hypovolemic shock, a concomitant mass lesion, coagulopathy, bleeding from dural or diploic veins, a dural sinus laceration, a traumatic pseudoaneurysm, or an arteriovenous fistula. Although criteria for computed tomography of patients with head injuries remain variable in the literature, delayed presentation of epidural bleeding must be considered in the differential diagnosis of posttraumatic headache irregardless of the time interval or neurological presentation.