Physical, motor, sensory and developmental features associated with agenesis of the corpus callosum.

BACKGROUND: The study objective was to develop a profile of characteristics and diagnostic indicators of agenesis of the corpus callosum (ACC) using a large sample of individuals with ACC and their siblings. Very few previous studies have been able to access large populations in order to develop a comprehensive profile. METHODS: Caregivers of 720 individuals with ACC and 219 siblings, the largest sample studied to date, provided surveys with data on diagnoses, physical characteristics, developmental patterns and physical functioning. RESULTS: Compared with siblings, individuals with ACC exhibited a pattern of delayed motor development, difficulty with balance and bimanual movements, large head size, poor muscle tone, poor depth perception, reduced pain perception, sleeping difficulties and an increased proportion of left and mixed handedness. CONCLUSIONS: These results extend previous descriptions but are also consistent with published reports that used small samples and single case studies. The data provide a profile that has implications for early detection and intervention of individuals with ACC as well as for highlighting future research directions to extend knowledge about ACC.

The stability of compromised interhemispheric processing in callosal dysgenesis and partial commissurotomy.

The persistence and stability of selective deficits in interhemispheric processing resulting from known callosal pathology have been monitored over periods ranging from ten to thirty five years. The present study included five patients: two with complete agenesis of the corpus callosum, one with partial dysgenesis, and two with a partial section of the corpus callosum. A crossed-uncrossed difference task and four bilateral visual matching tasks were administered to these patients and to groups of normal individuals matched on age and intelligence. As expected, all of the patients showed deficits in speed or accuracy relative to the performance of their control groups. The profile of performance for each patient across the five tasks demonstrated a systematic (but not perfectly consistent) relationship with the location and extent of callosal pathology.

The role of attention in visual bilateral matching tasks.

The consistent finding of studies employing visual matching tasks has been a reaction time and accuracy advantage for judgements about stimuli presented bilaterally when compared to the average performance of the two unilateral field presentations. As with recent studies showing the influence of attention on reaction times to unilateral presentations, we hypothesized that attentional mechanisms may also play a role in the speed advantage seen with bilateral letter presentations. The present study employed random dot-patterns ("dot-primes"), presented in the upper half of the LVF, RVF, Bilateral VF, or absent, as abrupt onset peripheral cues to attract attention automatically. Letter pairs followed immediately (14 msecs) after the dot-primes in the lower half of the LVF, RVF, or Bilateral VF. The results for unilateral dot-primes, followed by unilateral letter pairs, were consistent with previous studies showing that the field advantage for a particular task can be altered using abrupt onset attentional cues, with the advantage going to the field where the attentional prime is presented. Bilateral dot-primes did reduce latencies to subsequent bilateral letter pairs, but bilateral primes also reduced latencies to both LVF and RVF letter pairs, in nearly the same proportion as for bilateral letter pairs. Latencies for RVF-primes/Bilateral-letters were as fast as for Bilateral-primes/Bilateral-letters, and both of these conditions were significantly faster than LVF-primes/Bilateral-letters. The results suggest that attention plays a relatively minor role in the bilateral field advantage, and that non-attentional factors (i.e. interhemispheric dynamics) account for most of the asymmetric unilateral-prime influence on bilateral performance. Possible interhemispheric factors which may contribute to these results are discussed.

Interhemispheric transfer time differences related to aging and gender.

The difference in simple reaction times to unstructured stimuli contralateral to the hand used for response ('crossed' responses) and those stimuli ipsilateral to the hand used for response ('uncrossed' responses)--or crossed-uncrossed difference (CUD) is assumed to be a reliable index of interhemispheric transfer time (IHTT). Studies using the CUD paradigm with acallosal patients as well as a variety of populations with known variations in callosal size or functioning have demonstrated that such callosal differences are reflected in differences in recorded CUD times. Recent studies have suggested that elderly individuals show a reduction in size of the corpus callosum, particularly in the anterior region. In order to assess any potential change in callosal transfer efficiency with aging. CUDs were obtained from elderly (60+ years) and younger subjects (18 30 years). The elderly subjects showed a significantly elongated CUD compared to younger subjects, with elderly females contributing the greatest increase. No significant gender differences were found for younger subjects. In addition, an unexpected trend for an overall right field reaction time advantage was found for all subgroups, accompanied by a larger calculated CUD for right hand responses than for left hand responses.

[Superficial veins of the human spinal cord. An attempt at classification]. / Les veines superficielles de la moelle épinière chez l'homme. Essai de systématisation.

By studying the systematization of superficial veins in 70 human spinal cords, it is possible to recognize three different systems: anterior, posterior and lateral. The anterior spinal venous system is formed by an antero-medial trunk extending from the filum terminale to the medulla oblongata, and by two antero-lateral spinal trunks placed in the cranial part of the spinal cord. The posterior, spinal venous system is formed by a postero-medial spinal trunk, extending from the sacral spinal cord to the medulla oblongata, and by two postero-lateral venous trunks, in the thoracic region. The lateral spinal venous system forms an anastomotic system between the anterior and posterior venous systems; it is especially well developed in the lumbar enlargement. In this venous disposition, it can be recognized three types of networks: transversal, longitudinal and arciform, more or less intertwined according to the considered spinal levels.