Ring chromosome 17: phenotype variation by deletion size.

Ring chromosome 17 is a rare cytogenetic abnormality, with 12 previous reports in the literature. Some have a relatively mild phenotype characterized by seizures, mental retardation, skin changes and short stature. Other patients have Miller-Dieker syndrome (MDS), which includes lissencephaly, multiple dysmorphic features, severe mental retardation and shortened life expectancy. We describe two new cases of ring chromosome 17 and review the literature. Our cases and the other reports of patients without a deletion encompassing the Miller-Dieker region, delineate a fairly distinctive subgroup of individuals with ring 17, whose phenotype consists of growth and mental retardation, seizures, minor dysmorphic features, café-au-lait spots and retinal flecks. This classification of ring 17 into two distinct groups based on the size of the deletion and the phenotypic manifestations should facilitate clinical suspicion of this rare chromosomal abnormality.

Measurement of lingual and palatine somatosensory evoked potentials.

OBJECTIVE: A technique is presented for generating and recording lingual and palatine nerve somatosensory evoked potentials (SEPs). METHODS: Pairs of thin, stainless steel disk electrodes were mounted onto mandibular or maxillary acrylic splints, similar to orthodontic retainers. Mandibular splint electrodes were oriented to contact the under surface of the tongue along the course of the right and left lingual nerves and maxillary splint electrodes were oriented to contact the hard palate bilaterally along the course of the palatine nerves. SEP recording electrodes were placed on the scalp 1 cm posterior to C5 and C6 (C5' and C6', respectively) using the combinatorial nomenclature of the International 10-20 system. Two reference electrode locations, Fz and C5' or C6', over the cortical hemisphere opposite that of the recording electrode, were used. RESULTS: Right and left lingual and palatine nerve SEPs were recorded from five normal adults. SEP latencies were similar to the N13 and P18 cortical peak latencies recorded in previous studies of trigeminal nerve branches to the lips regardless of reference electrode position. CONCLUSIONS: A more precise method of stimulating the intraoral lingual and palatine nerves was accomplished using dental splints. SEPs were easier to obtain using a contralateral cortex reference electrode location.

Ictal cognitive assessment of partial seizures and pseudoseizures.

BACKGROUND: Previous studies suggest that responsiveness is impaired during complex partial seizures (CPS) and pseudoseizures (PS); however, to our knowledge, there has been no systematic comparison using both response and memory testing. OBJECTIVE: To compare CPS with PS using ictal cognitive assessment (ICA) of responsiveness and memory. PATIENTS AND METHODS: We used a nonautomated method of ICA by bedside observers, consisting of family members and staff, during video electroencephalographic monitoring to test responsiveness and memory during the ictal phase in 245 events. We assessed the adequacy of testing and compared the testing results in 31 patients during CPS and 13 patients during PS. RESULTS: The ictal presentation of a command was successful in 58% of the events. The ictal presentation of at least 2 memory items with testing for recall after orientation was adequate in 57% of events. Impaired responsiveness was shown during both CPS and PS. However, some response was detected during 48% of PS compared with 18% of CPS (P<.01). Memory items were recalled during 63% of PS but during only 4% of CPS (P<.001). The International Classification of Epileptic Seizures remained useful, but in 11 events (8%), distinguishing complex from simple partial seizures was difficult. Recall of various types of stimuli (aural-verbal vs visual-pictorial) during ICA did not correlate with the side or location of the seizure focus, but this may have been confounded by the rarity of any memory recall during CPS. CONCLUSIONS: Ictal cognitive assessment by bedside observers is practical and provides the interaction necessary for properly classifying seizures; ICA, especially memory, may help to distinguish CPS from PS.

Editing status at the Q/R site of the GluR2 and GluR6 glutamate receptor subunits in the surgically excised hippocampus of patients with refractory epilepsy.

The editing status of mRNA at the Q/R site of the glutamate receptor subunits GluR2 and GluR6 modulates channel conductivity and ion selectivity of ionotropic AMPA/KA receptors. Alteration of the editing process may be involved in the debilitating effects of epilepsy. The ratio of unedited/edited (Q/R) forms of GluR2 and GluR6 subunits was examined in conjunction with the expression of two double-stranded RNA-specific adenosine deaminases (DRADA) in surgically excised hippocampus from patients with refractory epilepsy compared with that of control samples. In the majority of patients with long histories of epilepsy, the GluR2 transcript was detected in the completely edited form, however, in two (out of 16 tested) hippocampal samples of young subjects (2 and 10 years old) we were able to identify the unedited transcript of GluR2 subunit. The proportion of unedited fraction of GluR6(Q) subunit was decreased to 9% compared to control human hippocampus. We conclude that the editing process in epileptic specimens is selectively affected by seizure activity in the epileptic focus.

Electrocerebral inactivity associated with obstructive sleep apnea.

We report a child who demonstrates near electrocerebral silence secondary to obstructive apnea during polysomnography. The mechanism of this suppression of cortical activity appears to be related to hypoxemia in the absence of a malignant arrhythmia.

Painful generalised clonic and tonic-clonic seizures with retained consciousness.

Two patients in whom consciousness and memory were retained during bilateral clonic or tonic-clonic seizures are reported on, and three patients reported on previously are reviewed. Ictal semiology differed from myoclonic and supplementary motor seizures, which are other seizure types characterised by bilateral motor movements and retained awareness. In the two new patients ictal pain was a prominent feature. It is proposed that propagation of seizure activity may be confined to the sensorimotor areas bilaterally while sparing the neural structures involved in maintaining consciousness and in processing language and memory. This unusual type of seizure may be misdiagnosed as a pseudoseizure. Detailed description of the ictal events and further laboratory evaluation including video-EEG monitoring may be necessary to make the distinction.

The threshold effects of Nd and Ho: YAG laser-induced surface modification on demineralization of dentin surfaces.

Laser irradiation alters the structure of dentin and produces surface layers that give the appearance of being more enamel-like. The laser-modified surface may be more resistant to demineralization; hence, many investigators are proposing continued development of the laser as a possible preventive treatment for caries. The purpose of this study was to explore the morphological changes that occur in dentin when treated at threshold illuminance with two clinically interesting laser wavelengths, and to evaluate the effectiveness of the laser-treated surface at resisting demineralization in an acid-gel solution. The Nd: YAG laser (wavelength 1060 nm) produced significant recrystallization and grain growth of the apatite, without the formation of second phases such as beta-tricalcium phosphate. This recrystallized surface layer showed resistance to demineralization; however, the layer did not provide protection of the underlying dentin from demineralization because of cracks and macroscopic voids that allowed for penetration of the demineralizing gel. The Ho: YAG laser-treated surface (wavelength 2100 nm) did not show significant evidence of recrystallization and grain growth, and only a trace amount of an acid-resistant layer was observed with demineralization. It is speculated that the Ho:YAG laser is coupling with absorbed water, and that the heat transfer from the water to the mineral phase is inefficient. For the purposes of creating a demineralization-resistant layer, threshold illuminance with both Nd: YAG and Ho: YAG was ineffective.

Lower brain-stem origin of the median nerve N18 potential.

A patient undergoing intraoperative median nerve somatosensory evoked potential (MSEP) and brain-stem auditory evoked response (BAER) monitoring showed changes during basilar artery aneurysm clipping. There was loss of the BAER wave V, with preservation of waves I and III. Simultaneously, there also was loss of the MSEP N20 potential, with preservation of the N18, N13 and Erb's point potentials. The patient died and autopsy showed an infarct involving the whole rostro-caudal extent of the pontine tegmentum. This combination of electrophysiologic and pathologic findings may help answer questions regarding the exact generators of different MSEP potentials. In particular, it implies that medullary structures can generate the N18 potential.

Reduced bioavailability of moisture-exposed carbamazepine resulting in status epilepticus.

A 28-year-old man with seizures well controlled with carbamazepine (CBZ) and valproate (VPA) developed generalized convulsive status epilepticus three days after his CBZ tablets became wet during a rainstorm while he was camping out. He continued the CBZ but avoided ingesting obviously disintegrating tablets. The VPA was not exposed to excessive moisture. Previous random CBZ blood levels had been in the range of 9-13 micrograms/ml; at the time of admission to the emergency room the level had decreased to 3.8 micrograms/ml. The VPA level did not change significantly from baseline. The moisture-exposed CBZ tablets were of expected weight but were swollen and enlarged. Analysis of these tablets by USP paddle method 2 demonstrated a mean dissolution of 16% at 60 min as compared with > 80% for fresh CBZ tablets. After final dissolution of the moisture-exposed CBZ tablets, normal quantities of active drug were noted. We propose that poor dissolution of moisture-exposed CBZ tablets results in reduced bioavailability. We urge caution in the packaging and storage of CBZ to avoid exposure to moisture.

Acquired aprosodia in children.

In adults, the affective components of language, including certain aspects of prosody and gesturing, appear to be a dominant function of the right hemisphere. The various combinations of affective processing deficits associated with focal right brain damage are called aprosodias and have functional and anatomical correlates similar to the propositional language deficits associated with aphasias secondary to focal left brain damage. Developmental affective-prosodic deficits have been reported recently in children with congenital or very early right hemisphere injury. We now report two school-aged children with acquired motor-type aprosodias following acute right focal brain injury. Their affective prosody and singing were also analyzed acoustically during the acute and recovery phases of illness. Based on these cases, we propose the term children aprosodia to describe affective-prosodic deficits that result from acquired lesions of the right hemisphere in children.