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Objective: To study the impact of competing risks on Hardy-Weinberg equilibrium and their consequences in case-control studies of gene-late onset disease association., Methods: Based on a population born in Hardy-Weinberg equilibrium for a particular gene, the genetic composition when the gene is associated with a lethal early-onset disease and its consequences on a late-onset disease can be deduced. Odds ratios estimates are unbiased in case-control studies when controls are sampled by density, even if the controls are in Hardy-Weinberg disequilibrium., Results: An example in which a mutant gene is associated with early mortality is presented, producing a departure from Hardy-Weinberg equilibrium; as a result, controls in later ages are in disequilibrium, producing an odds ratio equal to 1.61., Conclusion: Although the main causes of Hardy-Weinberg disequilibrium in controls are selection bias or genotyping error, a competing risk of death associated with the mutant gene would also result in Hardy-Weinberg disequilibrium among controls.

Malignant peripheral nerve sheath tumors (MPNST) are rare. We report a case of a MPNST of the proximal sciatic nerve in the thigh, unassociated with pre-existing type 1 neurofibromatosis or history of radiation therapy. A 71-year-old man had a 6 month history of constant, severe, burning pain affecting the sole of the left foot. One month after the onset, the pain radiated to the left calf, posterior aspect of the thigh and buttock, and distal leg weakness followed. Three months prior to admission, the patient developed a large and painful mass in the buttock, that occupied the entire left gluteal region on examination. There was severe weakness of ankle and toe dorsiflexion and plantarflexion, decreased sensation on the lateral and posterior aspect of the left leg as well as on the dorsal and plantar surfaces of the foot, and absent ankle jerk. EMG showed denervation and motor unit loss in the short head of biceps femoris and muscles supplied by tibial and peroneal nerves on the left side. Magnetic resonance imaging revealed a 10-cm enhancing mass of the left sciatic nerve from the upper thigh to the greater sciatic notch. In surgery, a large MPNST with a high Ki67 labeling index (> 60 %) was subtotally removed from the sciatic nerve, and adjuvant radiation therapy was administered. In the ensuing months the tumor invaded the entire pelvic region. A high sciatic malignant tumor can present with a rapidly growing buttock mass and unilateral, neuropathic foot pain imitating the tarsal tunnel syndrome.

Hereditary ataxias encompass a series of syndromes basically characterised by progressive cerebellar ataxia of slow clinical course (occasionally, periodic ataxia or spastic paraparesis) and primary spinocerebellar degeneration. The prevalence ratio of these syndromes in Spain is 20 cases per 100,000 inhabitants. Initially the ataxias were classified on the basis of clinicopathological criteria. Starting from the seminal papers by Harding published 20 years ago, a clinicogenetic classification was introduced that has given way to the present molecular classification. There have been localised about forty loci. In dominant ataxias the most frequent molecular defect is a dynamic CAG expansion responsible for abnormal polyglutamine tract transcription. The identification of such molecular defect has made it possible detection of gene carriers in clinical practice, this involving both presymptomatic and prenatal diagnosis; moreover, such molecular discoveries have contributed to develop a new pathogenetic era. A homozygous and intronic GAA expansion is the molecular basis of Friedreich's ataxia. This finding has also made it possible a molecular diagnosis in clinical practice. Molecular studies have demonstrated that hereditary spastic paraplegia is another heterogeneous genetic disorder.

Although the lingual nerve and the chorda tympani are the components of the classic peripheral gustatory pathway, loss of taste in patients after surgery for trigeminal neuralgia supports for the existence of an accessory gustatory pathway through the trigeminal sensory root and the gasserian ganglion. Bell's palsy is the most common pathology of the peripheral gustatory pathway. The central gustatory pathway ascends from the solitary tract nucleus in the medulla up to the upper pons in the ipsilateral central tegmental tract, rather than in the medial lemniscus as proposed in the past. It is not possible to specify whether the central gustatory pathway decussates or not at the lower midbrain level. Interruption of the gustatory pathway in the brainstem usually occurs with stroke or demyelination. The thalamic gustatory relay is located in the most medial aspect of the ventroposteromedial nucleus, immediately adjacent to the somatosensory area for the oral cavity and fingers. Therefore, ageusia associated with the sensory cheiro-oral syndrome may occur with a thalamic lesion. The laterality of the gustatory representation in the thalamus remains unresolved. Studies on epileptic gustatory aura have demonstrated that the insula and the anteromedial temporal lobe are the primary and secondary gustatory cortex, respectively. Taste perception results in patients with corpus callosum section and strokes or tumors involving the insula support the hypothesis that there is a gustatory representation of both hemitongues in the left cerebral hemisphere, whereas only the right hemitongue is represented in the right hemisphere.

Introduction and Objective: The objective of the study was to analyze the EEG tracings during the seizures of two monozygotic twins, shown on molecular analysis, diagnosed as having infantile epilepsy with absences. The recordings are particularly interesting since the genotypes of the patients are identical. This allowed comparison between the similarities and differences in discharges so that they could be better defined., Results: The 3 Hz spike and wave complexes were the same as the classical descriptions in typical absences. No 'W' spike and wave complexes morphology, discharge fragmentation or light induction of the discharges were observed. There was some differences in the duration of absences, which were much shorter in one twin girl. The duration of the seizures was variable, and sometimes similar to that described as characteristic in other types of generalized idiopathic epilepsies with absences. It would seem therefore that the duration of the seizure is not a criterion for differentiation between the different types of generalized idiopathic epilepsies., Conclusion: Concordance, both clinical and of seizure EEG recordings in our patients confirmed that there is a specific electroclinical phenotype in infantile epilepsy with absences, although individual variations may also occur.

Background: The aim of this study was to analyze the diagnostic distribution of patients consulting because of headache in a neurology department., Methods: The clinical records of 3,498 patients who had consulted specifically due to headache between 1978 to 1993 were retrospectively studied. Diagnosis was reclassified according to the criteria of the new headache classification with data concerning the age of onset and sex distribution also being collected., Results: The most frequent diagnoses were migraine (1,802 patients; 52%) tension-type headache (113; 32%), followed in decreasing order by trigeminal neuralgia, post injury headache, cluster headache, subarachnoid hemorrhage, analgesic-ergotamine abuse headache, tumoral headache, cervical disease headache, benign exertional headache, due to paranasal sinusal disorders and benign intracranial hypertension. Female predominance was observed in the whole series (68%) as in the groups with migraine, tension-type headache, neuralgia headache by analgesic-ergotamine drugs and benign intracranial hypertension. Cluster, post injury, tumor and provoked headaches (cough, exertional and sexual) were found to be more frequent in men. The age of onset was very specific for each kind of headache. The percentage of symptomatic headaches increased in direct relation to age, being 10 fold higher in patients over the age of 65., Conclusions: The diagnostic distribution of headache as a cause of medical consultation is very different to the prevalence of different headaches. This distribution by diagnosis largely depends on the age of the patient at the time of headaches onset [corrected].