Medical technology assessment photic stimulation--standardization of screening methods.

RATIONALE: In many EEG laboratories in Europe, intermittent photic stimulation (IPS) is not performed routinely, and consequently, great variation exists in the type of photo stimulator used, the methodology employed, and the interpretation of the EEG curves, thus leading to different outcomes. METHODOLOGY: It was decided to hold a consensus meeting with experts in the field of photic stimulation from various European countries. This meeting was held at the Stichting Epilepsie Instellingen Nederland, Heemstede, the Netherlands. The consensus reached was presented and discussed at the 9th European Congress of Clinical Neurophysiology in Ljubjana in June 1998. RESULTS: Patients should be positioned at a distance of 30 cm from the photic stimulator (nasion to lamp) with dim surrounding lights, just enough to see the patient. Flashes should be delivered in separate trains of 10 s for each frequency, with intervals of 7 s minimum. First stimulation occurs with eyes open followed after 5 s by eye closure, while starting at 1 Hz progressing to 20 Hz, unless generalised epileptiform discharges are evoked at a lower frequency. Then, frequencies should start at 60 Hz decreasing to 25 Hz. The following frequencies should be used: 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 60, 50, 40, 30 and 25 Hz. The total duration is a maximum of 6 min (patients without a reaction to IPS). In interpreting the evoked responses, a clear distinction should be made between epileptiform responses confined to the occipital area (OSW), starting occipitally and spreading to frontal regions (OGSW), or generalised from the start (GSW). Other responses include generalised spikes (OR). CONCLUSION: This standard is safe, relatively quick, simple and reliable. Comparison of data within patients and between patients of various laboratories will also be possible. This will improve the quality of the care of the individual patient and make collaborative research possible.

Analysis of GLRA1 in hereditary and sporadic hyperekplexia: a novel mutation in a family cosegregating for hyperekplexia and spastic paraparesis.

Hyperekplexia is a rare condition characterised by the presence of neonatal hypertonia and an exaggerated startle response. Mutations have been described in GLRA1, the gene encoding the alpha 1 subunit of the glycine receptor, in dominant families with hyperekplexia and in a single sporadic case, thought to represent an autosomal recessive form of the disease. In this study the coding region of the GLRA1 was analysed in eight probands with hyperekplexia by restriction digest and sequencing. Two familial cases were found to possess the previously described G1192A (R271Q) mutation in exon 6. In an additional family in which hyperekplexia cosegregates with spastic paraparesis, a novel A to G transversion at nucleotide 1206 in exon 6 was detected that changes a lysine at amino acid 276 to a glutamate (K276E). In four sporadic cases no mutations were found. In addition, one familial case did not have a mutation in the coding region of the gene.