Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027066 (myoclonus)
 4,275 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Startle disease is an autosomal dominant disorder with two phenotypic expressions. In the major form, there is hypertonia in infancy, and later an insecure gait. The patients have falling attacks without unconsciousness and in these, they are often injured or suffer concussions. Episodes of shaking of the limbs lasting for several minutes and resembling generalized clonus or repetitive myoclonus occur. These are most often nocturnal and are also unaccompanied by loss of consciousness. the patients are hyperreflexic and show an increased incidence of associated neurological and electroencephalographic abnormalities. The minor form of startle disease is only manifested by excessive startle and this is inconstant. In infancy it is brought out by febrile illness and in adult life by emotional stress. Gastaut and Villeneuve postulated the existence of a sporadic form of hyperekplexia different from the disorder described by Suhren et al. Review of their report and comparison with the cases of Suhren et al, and our own patients leads us to believe that the sporadic and familial forms of startle disease are the same. The disorder is rare, probably misdiagnosed initially as spastic quadriplegia, and later as epilepsy. Clonazepam appears to be the treatment of choice and its effect is sustained.
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PMID:Startle disease or hyperekplexia: further delineation of the syndrome. 677 25

Hyperekplexia is a hereditary neurologic disorder manifested by an exaggerated startle response, generalized muscular rigidity, and prominent nocturnal myoclonus. The distinctive features of this syndrome constitute an unusual clinical entity that is easily mistaken for other disorders. The study of a family provided additional data on various aspects of this condition. The proband was 3 months old when he was referred for persistent generalized stiffness since birth; this stiffness was associated with an exaggerated startle response and intermittent apnea. Similar symptoms in infancy and prominent nocturnal myoclonus with an excessive startle response in adulthood were described in other family members for five generations. Various features of the disorder indicate a relationship to the syndrome of the "jumping Frenchmen of Maine," latah, miryachit, and other unusual startle reactions.
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PMID:Hyperekplexia. 683 Apr 76

Hyperekplexia (startle disease) is an unusual, familial, neurological disorder characterized by abnormally enhanced startle response, followed in most cases by momentary generalized muscular stiffness. These attacks may cause the patients to fall rigidly, while remaining fully conscious. Startle symptomatology has generally an onset in infancy and is often accompanied, during the first years of life, by rigidity, sleep myoclonus, motor delay, regurgitation and apneic spells, which may cause sudden death. Stiff-baby syndrome is a familial disorder characterized by marked rigidity, with neonatal onset and gradual reduction during infancy, regurgitations, motor delay and attacks of stiffness. We report 4 new cases of hyperekplexia from two different families and another infant with stiff-baby syndrome discussing clinical, electrophysiological and genetic aspects of both neurological disorders in relation to other reported cases. We suggest a continuum between these familial syndromes, which are often misinterpreted as epilepsy or other disorders.
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PMID:Hyperekplexia and stiff-baby syndrome: an identical neurological disorder? 850 69

Hyperekplexia (startle disease) is a rare non-epileptic disorder characterised by an exaggerated persistent startle reaction to unexpected auditory, somatosensory and visual stimuli, generalised muscular rigidity, and nocturnal myoclonus. The genetic basis is a mutation usually of the arginine residue 271 leading to neuronal hyperexcitability by impairing glycinergic inhibition. Hyperekplexia is usually familial, most often autosomal dominant with complete penetrance and variable expression. It can present in fetal life as abnormal intrauterine movements, or later at any time from the neonatal period to adulthood. Early manifestations include abnormal responses to unexpected auditory, visual, and somatosensory stimuli such as sustained tonic spasm, exaggerated startle response, and fetal posture with clenched fists and anxious stare. The tonic spasms may mimic generalised tonic seizures, leading to apnoea and death. Consistent generalised flexor spasm in response to tapping of the nasal bridge (without habituation) is the clinical hallmark of hyperekplexia. Electroencephalography may show fast spikes initially during the tonic spasms, followed by slowing of background activity with eventual flattening corresponding to the phase of apnoea bradycardia and cyanosis. Electromyography shows a characteristic almost permanent muscular activity with periods of electrical quietness. Nerve conduction velocity is normal. No specific computed tomography findings have been reported yet. Clonazepam, a gamma aminobutyric acid (GABA) receptor agonist, is the treatment of choice for hypertonia and apnoeic episodes. It, however, may not influence the degree of stiffness significantly. A simple manoeuvre like forced flexion of the head and legs towards the trunk is known to be life saving when prolonged stiffness impedes respiration.
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PMID:Hyperekplexia in neonates. 1152 14

Differential diagnosis between epileptic and nonepileptic paroxysmal disorders is fundamental not only to allow correct management of patients but also to avoid the burden of unnecessary antiepileptic medication. The focus of this chapter is limited to imitators of idiopathic generalized epilepsies (IGE) which are expressed through myoclonic, tonic-clonic, tonic, atonic, and absence seizures. Apparent losses of consciousness and drop attacks also have to be considered. Benign myoclonus of early infancy is the main nonepileptic disorder in the differential diagnosis of infantile spasms, but is not dealt with here because West syndrome is not an IGE. Hyperekplexia, metabolic disorders, hypnagogic myoclonus, and disturbed responsiveness caused by the use of drugs are listed in Table 1. Other conditions that may imitate more focal epileptic seizures are omitted. Benign neonatal sleep myoclonus, apnea and apparent life-threatening events in infants, cyanotic and pallid breath-holding spells, syncope, staring spells, psychogenic seizures, hyperventilation syndrome, and narcolepsy have been selected based on frequency or difficulties in differential diagnosis with the intention to cover the most conspicuous imitators of IGE in different ages.
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PMID:Nonepileptic disorders imitating generalized idiopathic epilepsies. 1630 79

Hyperekplexia (MIM #149400) is a rare neurological disorder characterized by an exaggerated startle response, infantile hypertonia and hyperreflexia without spasticity, a hesitant gait that usually improves by 3 years of age, and nocturnal myoclonus. Familial hyperekplexia is usually autosomal dominant resulting from mutations in the inhibitory glycine receptor subunit alpha 1 (GLRA1) gene on chromosome 5q. We identified a 3-generation family with progressively severe phenotypes of hyperekplexia. All affected family members were found to be heterozygous for a novel arginine271proline mutation in GLRA1. Long-term follow-up of the affected members of the third generation, now aged 6 and 7 years, reveals enhanced startle responses and persistent hypertonia of the extremities without clonus or a catch, tight heel cords and abnormal toe-walking gait, and plantar flexor reflexes. The 7-year-old child recently reponded well to a benzodiazepine. Future studies are warranted to examine whether this new missense mutation is solely responsible for this atypical phenotype.
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PMID:A novel GLRA1 mutation associated with an atypical hyperekplexia phenotype. 1907 49

Hyperekplexia is a rare neurogenetic disorder characterized by startle. Accurate diagnosis of this notorious mimicker of epilepsy is important to prevent life-threatening apnoea. We report a novel case of concomitant GLRA1-related hyperkeplexia and myoclonic epilepsy. A toddler with daily paroxysms of head drops and falls presented with epileptic myoclonus on EEG, however, whole-exome sequencing revealed hyperekplexia-related GLRA1 mutation. The boy eventually developed spells induced by noise and surprise. All his spells remitted upon treatment with clonazepam. Paediatricians and paediatric neurologists should be aware of this possible mixed presentation in order to appropriately tailor medication regimens and treatment goals. [Published with video sequence on www.epilepticdisorders.com].
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PMID:A child with hyperekplexia and epileptic myoclonus. 3007 84

Non-epileptic paroxysmal disorders are frequent events in the neonate, generally transient. However, due to their intensity they can be confused as true epileptic seizures. The objective of this review is to update the concepts in relation to tremors, neonatal benign sleep myoclonus (MNBS) and hyperekplexia. The tremors are very frequent, once identified it must be determined if they belong to a hyperexcitability syndrome related to maternal or perinatal factors, in idiopathic cases a good prognosis is expected. MNBS are often confused with epileptic seizures. They are characterized by the fact that myoclonus is brief and occurs only in sleep, children are normal, and the EEG is also normal. Hyperekplexia is a rare, genetically determined disorder characterized by hypertonia and exaggerated startle reactions to a banal stimulus, which can be improved with clonazepam.
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PMID:[Non-epileptic paroxysmal disorder in neonates]. 3019 64