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Somatosensory evoked potentials with a unilateral migration disorder of the cerebrum
1Department of Child Neurology, National Center Hospital for Mental, Nervous, and Muscular Disorders, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan.
Insights
Somatosensory evoked potentials reveal altered sensory cortex function in children with unilateral brain malformations. Pachygyria impacts early cortical responses, suggesting dysfunction in affected sensory areas.
Area of Science:
- Neuroscience
- Clinical Neurology
- Developmental Neuroscience
Background:
- Unilateral brain malformations, such as pachygyria, can affect neurological function.
- Assessing sensory cortex function is crucial for understanding developmental disorders.
Observation:
- Two children with MRI-confirmed unilateral pachygyria were studied.
- Patients presented with hemiparesis, and in one case, seizures and mental retardation.
- No distinct sensory disturbances were noted in either child.
Findings:
- Short-latency somatosensory evoked potentials showed an absent N20 component with a positive wave upon stimulation of the paretic hand.
- Stimulation of the non-paretic hand yielded near-normal primary evoked responses in the affected hemisphere.
- Scalp recordings indicated a positive wave posterior to the central sulcus during stimulation of the paretic limb.
Implications:
- The findings suggest that malformed cortical areas in unilateral pachygyria may exhibit subnormal sensory function.
- Abnormalities in early somatosensory evoked potential components may indicate underlying cortical dysplasia.
- This study highlights the utility of somatosensory evoked potentials in evaluating sensory cortex function in pediatric neurological disorders.
Abstract:
The somatosensory evoked potentials in two children with a unilateral migration disorder (pachygyria) of the cerebrum, which was detected by MRI, were examined in order to evaluate the function of the malformed sensory cortex. A 5-year-old girl had slight left hemiparesis, seizures, and mental retardation, and a 4-month-old boy had left hemiparesis. Neither patient showed distinct sensory disturbance. Short latency somatosensory evoked potentials and somatosensory evoked potentials recordings demonstrated that the early cortical component, N20, was absent and a positive wave appeared on paretic left-hand stimulation. On nonparetic right-hand stimulation, the primary evoked response (N20-P30) of the left hemisphere, which originates in Broadmann area 3b, was almost normal. Multichannel recordings on the scalp of one patient revealed that a positive wave without polarity inversion appeared posterior to the right central sulcus on median nerve stimulation on the paretic side. The radial dipole in the sensory cortex (area 1 or area 3a) or motor cortex (area 4) could have formed the positive/negative biphasic wave in the relatively wide centroparietal area in the present patients. In the case of unilateral cortical dysplasia, the malformed cortex with subnormal function of sensation might induce the change in the early component of somatosensory evoked potentials.