Febrile myoclonus: an underreported, benign condition in infancy often misinterpreted as febrile seizures

Febrile seizures: an overview

Background

Febrile seizures are the most common neurologic disorder in childhood. Physicians should be familiar with the proper evaluation and management of this common condition.

Objective

To provide an update on the current understanding, evaluation, and management of febrile seizures.

Methods

A PubMed search was completed in Clinical Queries using the key terms ‘febrile convulsions’ and ‘febrile seizures’. The search strategy included meta-analyses, randomized controlled trials, clinical trials, observational studies, and reviews.

Results

Febrile seizures, with a peak incidence between 12 and 18 months of age, likely result from a vulnerability of the developing central nervous system to the effects of fever, in combination with an underlying genetic predisposition and environmental factors. The majority of febrile seizures occur within 24 hours of the onset of the fever. Febrile seizures can be simple or complex. Clinical judgment based on variable presentations must direct the diagnostic studies which are usually not necessary in the majority of cases. A lumbar puncture should be considered in children younger than 12 months of age or with suspected meningitis. Children with complex febrile seizures are at risk of subsequent epilepsy. Approximately 30–40% of children with a febrile seizure will have a recurrence during early childhood. The prognosis is favorable as the condition is usually benign and self-limiting. Intervention to stop the seizure often is unnecessary.

Conclusion

Continuous preventative antiepileptic therapy for the prevention of recurrent febrile seizures is not recommended. The use of intermittent anticonvulsant therapy is not routinely indicated. Antipyretics have no role in the prevention of febrile seizures.

Recent advances in febrile seizures

Febrile seizures are the most common seizures of childhood. A family history of febrile seizures is common, and the disorder is genetically heterogenous. While guidelines are available for management of simple febrile seizures, the management of complex febrile seizures is individualised. After a febrile seizure, it is important to rule out CNS infection and the decision to perform a lumbar puncture should be based on the clinical condition of the child. Neuroimaging and EEG are not required immediately in workup for simple or complex febrile seizures. Recurrence of febrile seizures may be managed at home by the parents with benzodiazepines. If the recurrences are multiple or prolonged and parents are unable to give home treatment, intermittent benzodiazepine prophylaxis may be given. Continuous antiepileptic prophylaxis may be given only to the children where intermittent prophylaxis has failed. Febrile seizures are also associated with increased risk of epilepsy, but this cannot be prevented by any form of treatment. There is also an increased risk of mesial temporal sclerosis, but whether this is an effect or cause of febrile seizures is as yet unclear. There is no increase in neurological handicaps or mortality following febrile seizures.

Isolated transient myoclonus in the elderly: an under-recognized condition?

BACKGROUND

Cases of transient myoclonus without other neurological manifestations in the elderly have very rarely been reported.

OBJECTIVE

To report clinical features of elderly people with isolated transient myoclonus.

METHODS

Clinical and laboratory features of 11 consecutive patients with isolated transient myoclonus (six men and five women; mean age, 75 years) were reviewed. Transient myoclonus was defined as an acute onset of tremulous myoclonus with/without asterixis in adults without other neurological symptoms.

RESULTS

Preceding infections were recorded in five patients (pneumonia, two; upper respiratory tract infection, two; and septic arthritis of the shoulder, one). Myoclonus predominantly affected the head and/or neck (n=10) and upper extremities (n=11), compared with the trunk (n=2) and lower extremities (n=6). Asterixis was observed in six patients. Laboratory testing, neuroimaging, and electroencephalograms revealed no specific abnormalities. With or without treatment using benzodiazepines, myoclonus in all patients resolved completely within 1-4 days, although five had recurrence 2-19 months after their first episodes. Among these five patients, the accompanying asterixis patterns (presence or not) in four were different in the first and subsequent episodes.

CONCLUSIONS

Isolated transient myoclonus with or without asterixis may be more common than generally believed, and it could be a clinical entity or disease spectrum. Transient myoclonus is a benign condition in the elderly, but can be under-reported or misdiagnosed. Therefore, it is important to recognize that the elderly may have this syndrome.

Febrile myoclonus: a missed clinical diagnosis

Myoclonic jerks presenting with fever have only rarely been reported and have often been misdiagnosed as febrile seizures. The presentation may be dramatic enough to provoke unnecessary investigation and treatment. Considering the benign nature of this condition, it is important that the condition is recognized by the physician so that hospitalisation and diagnostic procedures such as lumbar puncture and electroencephalogram are prevented. The authors report three cases of febrile myoclonus and review the subject.