No abstract

Theories concerning the etiology of attention deficit hyperactivity disorder have evolved from the 1950s, when it was believed that an injury to or dysfunction of the diencephalon was the cause of the syndrome, to the present day, when delayed brain maturation is postulated as an explanation. Delay in laying down myelin can be investigated by newly developed techniques like computerized EEG and transcranial magnetic stimulation. In this study, a group of 15 children 3-7 years of age suffering from attention deficit were investigated using both methods in combination and were compared to a control group of 23 age-matched normal children. On the computerized EEG spectral analysis significant differences to the control group were found in areas O1 and O2 (P < 0.05, Student's t-test). With transcranial magnetic stimulation, the overall difference in right/left stimulation was statistically significant (P < 0.001). The results suggest delayed myelination at the brain stem reticular formation where the alpha rhythm is activated and at the corticospinal pathway as parts of a widespread involvement.

Sirs: The blink reflex (BR) test evaluates the integrity of the trigeminalfacial arc. Unilateral electrical stimulation of the supraorbital nerve evokes two separate contractile responses in the orbicularis oculi muscle. The early (R1) component is evoked only on the side of stimulation as a pontine reflex, whereas the late (R2) component is recorded bilaterally and is presumed to be relayed through polysinaptic pathways of the pons and the lateral medulla. We report a case of trigeminal hypoesthesia with abnormalities in the BR demonstrative of a pontine lesion which was correlated with the lesion identified by magnetic resonance imaging (MRI).A 38-year-old woman was diagnosed as suffering from myasthenia gravis. She had a positive tensilon test, decremental response to repetitive stimulation of the cubital nerve, positive single-fiber electromyography in the extensor digitorum communis muscle, and positive anti-acetylcholine receptor antibodies. Her clinical evolution showed tactile hypoesthesia with dysesthesias in the three branches of the right trigeminal nerve to the vertex. Examination showed a tactile sensory deficit in the territory of this nerve with absent corneal reflex. There was no motor involvement. The remainder of the neurological examination was normal. The following neurophysiological tests were carried out: BR, somatosensory evoked potentials (SEPs) on both trigeminal nerves and brainstem auditory evoked potentials (BAEPs). BR recordings (Fig. 1) showed an absent R1 component to right supraorbital nerve stimulation, with normal R2 components latencies bilaterally and a normal latency of R1, R2I, and R2, C components to left supraorbital nerves stimulation. The SEP of the left trigeminal nerve was normal (P1:20 ms). No response to stimulation of the right side was be recorded. BAEPs showed a 0.4-ms relative prolongation of the III-V interpeak latency to right ear stimulation. Based on the results of the electrophysiological tests a subsequent cranial MRI was performed which showed an area of high signal intensity approximately 4.2 mm in diameter in the caudal part of the right pontine tegmentum (Fig. 2). This lesion corresponded to the location of the principal trigeminal sensory nucleus and spared the intra-axial mixed sensory and motor trigeminal nerve fascicles. This is a case of Kimura's third pattern [7]. The restriction of the BR abnormality to the R1 component in-LETTER TO THE EDITORS Fig. 1 A, B Blink reflex. A Absence of R1 in the right side with normal R2I and R2 C. B Normal R1, R2I, and R2C in the left side