Epilepsia partialis continua and defects in the mitochondrial respiratory chain

Epilepsia partialis continua (EPC) is characterized by continuous myoclonic or clonic jerks repeated at short intervals followed by a slowly progressive neurological disorder. We report three patients with EPC and a defect in the mitochondrial respiratory chain. METHODS: Clinical, neuroradiological, and biochemical data were reported. RESULTS: The patients presented continuous myoclonic jerks at age of 8 months, 11 months and 6 years, respectively. Two of the three patients had a previous developmental delay. Neurological examination at first admission revealed extrapyramidal symptoms in all patients. Initial biological investigations suggested mitochondrial dysfunction. Initial EEG showed a continuous discharge of periodic spikes (0.5-1Hz). MRI studies were initially normal then progressed to cerebral hemiatrophia. EEG revealed both correlation and absence of correlation between spikes or sharp waves and myoclonic jerks. The activity of one or several complexes of the mitochondrial respiratory chain was reduced in the muscle samples of the three patients. No mutation of mtDNA was found. CONCLUSION: Our report suggests that EPC can be due to mitochondrial respiratory chain disorders. Some clinical findings and initial investigations were indicative of a disorder of mitochondrial metabolism. Previous developmental delay, extrapyramidal symptoms and other organ involvement should suggest a possible mitochondrial etiology of EPC. In case of infant presenting EPC, mitochondrial respiratory chain disorder should be considered first.     

The use of the ketogenic diet in a patient with subacute sclerosing panencephalitis.

OBJECTIVE: To report on the effects of the ketogenic diet on a 9-year-old boy with myoclonic jerks due to subacute sclerosing panencephalitis (SSPE). METHODS: A 9-year-old boy presented with progressively worsening myoclonus unresponsive to valproic acid and clonazepam. He was started on the ketogenic diet maintaining urine ketones at greater than 80 mg x dl(-1). RESULTS: Within 2 weeks of dietary initiation, myoclonic jerks stopped. Four weeks later he developed cognitive slowing. Results of electroencephalogram and cerebrospinal fluid analysis were consistent with SSPE. Three months after ketogenic diet initiation, myoclonic jerks reappeared and were refractory to treatment. CONCLUSION: The ketogenic diet may be useful in controlling, even temporarily, the myoclonic jerks of SSPE.     

Subacute sclerosing panencephalitis presenting with unilateral periodic myoclonic jerks

BACKGROUND: Subacute sclerosing panencephalitis (SSPE) is a rare complication of measles virus infection. The disease is characterized by behavioural abnormalities, intellectual deterioration, motor weakness, and generalized myoclonic jerks progressing to coma and death in one to two years in 80% of the cases. The myoclonic jerks are associated with characteristic generalized slow periodic complexes on electroencephalography (EEG). The symptoms and signs of SSPE are frequently quite variable. The clinical course is equally variable and difficult to predict. The characteristic periodic myoclonus can rarely occur unilaterally particularly in the early stages of the disease. As well, the periodic EEG complexes have been reported unilaterally in up to 3% of cases. CASE REPORT: A 12-year-old boy, who was seen at a later stage with atypical manifestation of myoclonic body jerks confined entirely unilaterally, combined with contralateral periodic EEG complexes. One could assume clinically that the more diseased hemisphere was responsible for generating the jerks. However, brain magnetic resonance imaging revealed asymmetric hemispheric changes suggesting that the less neurologically damaged hemisphere is responsible for generating the unilateral myoclonic jerks. This has led to the interpretation that the more severely damaged hemisphere has lost the neuronal connectivity required to generate these periodic myoclonic jerks. CONCLUSIONS: Subacute sclerosing panencephalitis may have asymmetric hemispheric involvement, not only early, but also in the advanced stages of the disease, which can result in unilateral periodic myoclonic jerks.     

Cortical reflex myoclonus studied with cortical electrodes.

OBJECTIVE: To study the mechanism of cortical reflex myoclonus. METHODS: A patient with stimulus sensitive myoclonus of the left foot had an array of subdural electrodes placed over the right sensorimotor cortex. RESULTS: Stimulation through one of the electrodes (contact 13) facilitated leg muscles with the shortest latency and was presumed to lie over the motor cortex. Tibial nerve stimulation evoked a potential with the shortest latency 1 cm further posteriorly (contacts 11-12). These contacts were presumed to lie over the sensory cortex. The potential at 11-12 was followed by a much larger potential that reversed polarity at contact 13. Back averaging from spontaneous myoclonic jerks showed a cortical premovement potential which reversed polarity at contact 13. The threshold for the motor evoked potential in leg muscles evoked by transcranial magnetic stimulation was lower on the affected side. Electrical stimulation through contact 13 produced cortical potentials that could be recorded at adjacent contacts. The combination of a positive potential followed by a negative potential recurred at approximately 35-40 ms intervals, each positive potential generating a myoclonic jerk. Additional waves resembling I waves accompanied only the first positive potential. Surgical removal of the cortex under electrode 13 abolished the myoclonus. CONCLUSIONS: The myoclonic jerks arose in the motor cortex. We postulate that there is increased excitability or synchronization of the cortical neurons at that site. The spontaneous, peripherally induced and recurrent cortical potentials and myoclonic jerks can occur without participation of the circuitry of the presumed I waves.     

Photosensitive benign myoclonic epilepsy in infancy

PURPOSE: To describe the electroclinical features of subjects who presented with a photosensitive benign myoclonic epilepsy in infancy (PBMEI). METHODS: The patients were selected from a group of epileptic subjects with seizure onset in infancy or early childhood. Inclusion criteria were the presence of photic-induced myoclonic seizures and a favorable outcome. Cases with less than 24 month follow up were excluded from the analysis. RESULTS: Eight patients were identified (4 males, 4 females). Personal history was uneventful. All of them had familial antecedents of epilepsy. Psychomotor development was normal in 6 cases, both before and after seizure onset. One patient showed a mild mental retardation and a further patient showed some behavioral disturbances. Neuroradiological investigations, when performed (5 cases), gave normal results. The clinical manifestations were typical and could vary from upward movements of the eyes to myoclonic jerks of the head and shoulders, isolated or briefly repetitive, never causing a fall. Age of onset was between 11 months and 3 years and 2 months. Characteristically, the seizures were always triggered by photic stimulation. Non photo-induced spontaneous myoclonic attacks were reported in 2 cases during the follow-up. Other types of seizures were present at follow-up in 2 cases. The outcome was favorable, even if, usually, seizure control required high AED plasma levels. Since the clinical symptoms were not recognized early, some patients were treated only many years after the onset of symptoms. CONCLUSION: Among BMEI patients, our cases constitute a subgroup in which myoclonic jerks were always triggered by photostimulation, in particular at onset of their epilepsy.     

Progressive myoclonic encephalopathy in X-linked hypogamma-globulinemia. Case report, review of the literature and its relationship with progressive encephalopathy in children with A.I.D.S

A 7-year-old boy suffering from X-linked hypogammaglobulinemia and progressive myoclonic encephalopathy is reported. The onset of neurological disturbances is at four years of age with ataxic gait and myoclonic jerks. The EEG shows a progressive slowing of background activity, bilateral diffuse and repetitive, pseudoperiodic, high amplitude slow waves, myoclonic jerks polygraphically documented. The CT-scan shows generalized cerebral atrophy, white matter hypodensity--principally in the frontal regions -, multiple nodular calcifications, also in the basal ganglia. Two years after the onset of neurological signs, the boy is completely bedridden, spastic, dement and blind; the myoclonic jerks persist. Finally the relationship is discussed with both the previously reported patients with the same affection, and with similar progressive encephalopathy in children suffering from A.I.D.S.     

Axial myoclonus in paraproteinemic polyneuropathy

We describe a patient with a paraproteinemic anti-myelin-associated glycoprotein (anti-MAG) antibody polyneuropathy and concomitant axial myoclonic jerks. Neurophysiological investigation revealed that axial jerks were asymmetrical and exaggerated by lying in bed. They disappeared during mental arousal and sleep. Analysis of axial myoclonus showed that the first activated muscle was the left rectus abdominis with subsequent rostral and caudal propagation of a propriospinal type. Plasmapheresis substantially reduced the frequency and intensity of axial myoclonic jerks. In our patient, propriospinal myoclonus was associated with anti-MAG polyneuropathy, but the causal relationship remains unclear.     

Central pathway of photic reflex myoclonus.

Direct, new evidence for the cortical origin of photic reflex myoclonus in a patient with "posterior cortical atrophy" is provided. Photic stimulation elicited myoclonic jerks in the right upper limb muscles. An H2(15)O-PET activation study with photic stimulation showed increased regional cerebral blood flow not only in both striate cortices but in the left premotor and primary motor areas as well. Transcranial magnetic stimulation over the area of the left occipital cortex elicited motor evoked potentials in the right upper limb muscles. It is concluded that in the central pathway of photic reflex myoclonus the contralateral occipital cortex is activated first, then the impulses propagate intrahemispherically to the primary motor cortex, to elicit myoclonic jerks.     

Cortical myoclonus in Janz syndrome.

OBJECTIVE: To evaluate the characteristics of EEG paroxysms and the relationship between EEG spikes and ictal myoclonic jerks in patients with juvenile myoclonic epilepsy (JME). METHODS: Six patients with a typical form of JME entered the study and underwent computerized polygraphic recordings. In each patient, the inter-peak spike interval was measured on repeated EEG bursts, and jerk-locked back averaging was performed on ictal epochs using a time window including the 100 ms before and the 100-200 ms after the point at which the jerk-related EMG potential diverged from baseline. RESULTS: In all cases, the myoclonic jerks were associated with polyspike waves (PSW) complexes. The frequency of repeated spikes within the PSW complex ranged from 16 to 27 Hz. Jerk-locked averaging revealed a positive-negative EEG transient with maximal amplitude on the frontal leads, which preceded the myoclonic jerk by 10.25+/-0.96 ms. A delay of 9.50+/-1.73 ms was measured between the jerk-locked positive peak detected on the frontal EEG leads of the two hemispheres; a comparable time lag was observed between the onset of myoclonic jerks in the two deltoid muscles. CONCLUSIONS: Our data suggest that the ultimate mechanism responsible for ictal myoclonic jerks in JME is largely similar to that sustaining cortical myoclonus in more severe pathological conditions such as progressive myoclonus epilepsies, despite the different pathogenic substrate and triggering mechanisms.     

Influence of cholinergic system on myoclonus in myoclonic epilepsies.

The effect of two drugs upon multifocal myoclonic jerks was evaluated. The drugs influence the central cholinergic system in opposite ways. Eight patients with progressive and nonprogressive myoclonic epilepsy were tested. The single blind test was used. The number of myoclonic jerks after intravenous physostigmine (mean dose 0.02 mg/kg) and that after atropine (0.04 mg/kg) was compared to number of myoclonic jerks in the drug-free periods and with placebo. Placebo was without an effect. Physostigmine slightly increased the number of jerks. Atropine decreased the number significantly. In most patients the results were not striking. It is suggested that the cholinergic system may participate in the physiopathology of the studied myoclonus in a rather indirect, perhaps modulating way.     

Rhythmic cortical myoclonus in Niemann-Pick disease type C.

We here describe a patient with late-infantile Niemann-Pick disease type C (NPC) presenting with worsening myoclonus, seizures, cerebellar symptoms, mild mental impairment, and gaze palsy. Electroencephalographic (EEG) -polymyographic examinations showed abnormally high and diffuse background alpha-activity, enhanced by intermittent photic stimulation. The electromyographic (EMG) showed quasirhythmic myoclonic jerks during motor activation. EEG-EMG frequency analysis (better than jerk-locked back-averaging) demonstrated the cortical origin of the myoclonus. Our observations indicate that cortical myoclonus may occur as the main symptom of NPC.     

Fulminating adult-onset subacute sclerosing panencephalitis in a 49-year-old man

CONTEXT: Subacute sclerosing panencephalitis (SSPE) is a rare, slow viral infection caused by a defective measles virus. It is characterized by progressive mental deterioration associated with motor impairment and prominent myoclonus. In about 10% of all cases, the disease can progress rapidly and lead to death within a few months. The oldest previously reported fulminating case was in a 25-year-old man. OBJECTIVE: To emphasize the relationship between retinal involvement and acute SSPE by reporting the case of a 49-year-old man with clinical, laboratory, and pathological evidence of acute SSPE. SETTING: H?pital de l'Enfant-Jésus, Quebec, Quebec. REPORT OF A CASE: This man was referred to the Department of Neurological Sciences on March 21, 2001, because of recent behavioral changes and progressive cognitive impairment over the past few months. Medical history was unremarkable except for an episode of measles in his childhood. Neurological examination showed bilateral myoclonic jerks. Ophthalmic examination revealed bilateral macular swelling and papilledema. Electroencephalography showed periodic sharp and slow-wave discharges. Magnetic resonance imaging showed bilateral diffuse T2-signal hyperintensities in both periventricular and subcortical white matter. Cerebrospinal fluid antimeasles antibody titers were highly positive. An Omaya reservoir was inserted and therapy using a combination of high-dose intrathecal interferon alfa and oral isoprinosine were administered for 6 weeks. Despite transient subjective improvement in the patient's condition, it continued to deteriorate, he became bedridden, and he died on June 26, 2001. CONCLUSION: To our knowledge, this patient is the oldest case of SSPE reported in the literature. This patient and other patients with acute SSPE associated with bilateral macular swelling described in the literature raised the possibility of measles virus-acquired virulent neurotropism in the retina before invading the central nervous system.     

Dipole source localization in a case of epilepsia partialis continua without premyoclonic EEG spikes

A 72-year-old woman with epilepsia partialis continua (EPC) of the right foot is presented. Rhythmic myoclonic jerks were localized to the 1st and 2nd toes of the right foot and persisted for 72 h. EEG/video monitoring did not show any epileptiform transient in association with myoclonic jerks. MRI and MRA demonstrated an arterio-venous malformation involving the left fronto-parietal parasagittal area. Using the EMG signal from the myoclonic jerk we back-averaged the EEG 640 msec before and after the onset of the twitch. A negative-positive deflection was observed preceding the myoclonic jerks by 128–188 msec. Voltage topographic mapping showed a negative maximum in the left centro-parietal region. A multiple spatio-temporal dipole model was applied to the back-averaged deflection preceding the myoclonus. The patient's MRI was used to determine the center of the best fitting sphere, and the model was corrected accordingly. The best dipole solution consisted of 3 dipoles localized in the parasagittal frontal cortex, in the location of the motor representation for the foot. The utilization of a combined technique of back-averaging from the myoclonus and dipole source localization supported the epileptogenic etiology in this case.     

Progressive dialytic encephalopathy

A subacutely progressive dialytic encephalopathy lasting for three to 15 months in 11 patients who had been on haemodialysis for 14 to 36 months was characterized by dementia, language disorder, myoclonic jerks, behavioural disturbance, distinctive EEG abnormalities, and normal or nonspecific neuropathological findings.     

Clinical and Neurophysiological Development of Unverricht-Lundborg Disease in Four Swedish Siblings

Four siblings aged 12-18 years with progressive myoclonus epilepsy demonstrated a subclinical stage at the age of 9-11 years, with visual blackouts and polyspike electroencephalographic (EEG) activity on photic stimulation, an early myoclonic stage at the age of 12-15 years, with increasing segmental, stimulus-sensitive myoclonus, occasional nocturnal buildup myoclonic "cascade" seizures, slowing of EEG alpha-activity, episodic 4-6 Hz bilateral sharp waves and polyspikes with myoclonias on photic stimulation, and a disabling myoclonic stage at the age of 16-18 years, with periodic generalized myoclonias, nocturnal myoclonic "cascade" seizures, ataxia, dysarthria, mental changes, intermittent wheelchair dependency, and continuous EEG slow waves with polyspikes and intense myoclonias on photic stimulation. One of the siblings died at the age of 18 years with no apparent cause of death. Treatment with antiepileptic drugs other than valproate may have contributed but none of the siblings were ever treated with phenytoin. Extensive clinical and laboratory investigations revealed no abnormalities and excluded other known possible causes of progressive myoclonus epilepsy. The diagnosis was consistent with Unverricht-Lundborg disease and rested on typical age of onset, clinical signs, EEG, and evoked response abnormalities. Buildup myoclonic seizures are typical in advanced stages of Unverricht-Lundborg disease. We have labeled these myoclonic "cascade" seizures. A typical seizure was studied with video-EEG and cardiorespiratory monitoring. Characteristics revealed were onset with continuous arrhythmic myoclonic jerks followed by intense rhythmic myoclonus with increasing muscle tone that successively reduced the amplitude of the jerks. The EEG during the whole seizure showed intense polyspike activity. Obstructive apnea was seen at the peak of the seizure. There were no cardiac dysrhythmias. Consciousness was normal or only slightly impaired. Postictal drowsiness was not observed. Myoclonic "cascade" seizures are easily confused with generalized tonic-clonic seizures.     

Myoclonus and sensorimotor integration in a patient with Ramsay Hunt syndrome.

Clinical and neurophysiologic studies were done on a patient with action myoclonus secondary to Ramsay Hunt syndrome (dyssynergia cerebellaris myoclonica). Myoclonic jerks in the arms were much more common during movements directed to a target than in other movements. They appeared to be triggered primarily by external sensory inputs relevant to the movement rather than by the motor activity itself. Both somatosensory and visual inputs appeared able to trigger the myoclonic jerks. Myoclonic jerks in the deltoid muscle followed finger contact with a target by approximately 100 msec. Electrical stimuli delivered to the fingers during a reaching movement also triggered myoclonic jerks with a similar latency and also evoked giant cortical potentials which preceded the myoclonic jerks in deltoid by 15-20 msec. Our results suggest that during sensory guided movements, sensory inputs relevant to successful completion of the movement may have access to motor systems controlling the muscles involved. In our patient, who likely has lesions involving the cerebellar nuclei and/or cerebellar cortex, these sensory inputs appeared to result in an excessive motor response, possibly through mechanisms involving cerebellar-motor cortex connections.     

Clinical and genetic heterogeneity in benign hereditary chorea

BACKGROUND: Benign hereditary chorea (BHC) is an autosomal dominant disorder that can be distinguished from Huntington disease by its early onset, stable or only slightly progressive course, and absence of mental deterioration. The variation in clinical features is such that its very existence has been doubted. The authors recently described the localization of a gene responsible for BHC on chromosome 14q in a large Dutch family. OBJECTIVE: To report results of extensive clinical and linkage analyses for this Dutch family and six other families with BHC. RESULTS: Three of the seven families had linkage to a region on chromosome 14q13.1-q21.1. HOMOG analysis showed odds of 10 x 10(11) in favor of locus heterogeneity. Haplotype analyses for the linked families resulted in a reduction of the critical interval for the BHC gene to 8.4 cM between marker D14S49 and marker D14S278. Clinically, these three families had a homogeneous picture with early-onset chorea, sometimes accompanied by slight ataxia in walking, but without dystonia, myoclonic jerks, or dysarthria. The severity of the choreatic movements tended to abate in adolescence or early adulthood. In the unlinked families, symptoms and signs were more heterogeneous as to age at onset and the occurrence of myoclonic jerks or dystonia. CONCLUSIONS: BHC is a clinically and genetically heterogeneous disorder, with one well-defined clinical syndrome mapping to chromosome 14q.     

Chronic high-frequency deep-brain stimulation in progressive myoclonic epilepsy in adulthood--report of five cases

Purpose: To assess the efficacy and tolerability of chronic high‐frequency deep brain stimulation (DBS) in adult patients with progressive myoclonic epilepsy (PME) syndromes. Methods: Five adult patients (four male, 28–39 years) with PME underwent chronic high‐frequency DBS according to a study protocol that had been approved by the local ethics committee. Electrodes were implanted in the substantia nigra pars reticulata (SNr)/subthalamic nucleus (STN) region in the first patient and additionally in the ventral intermediate nucleus (VIM) bilaterally in the following four cases. Follow‐up took place in intervals of 3 months and DBS effects were compared with baseline frequency of passive and activation‐induced myoclonic jerks and daily life performance 8 weeks prior to implantation. Key Findings: Follow‐up periods ranged from 12–42 months (median 24 months). The best clinical effects were seen with SNr/STN DBS in all patients. VIM stimulation failed to achieve acute therapeutic effects and revealed low side‐effect thresholds and even triggering of myoclonia. In all patients the reduction of myoclonic seizures was observed and ranged between 30% and 100% as quantified by a standardized video protocol. All patients reported clinically relevant improvements of various capabilities such as free standing and walking or improved fine motor skills. In one patient with an excellent initial response generalized tonic–clonic seizures increased after 3 months of stimulation following extensive trauma‐related surgery. The best effect was seen in the least impaired patient. Significance: DBS of the SNr/STN may be an effective treatment option for patients with PME. Less impaired patients may benefit more markedly.     

Toxic encephalopathy due to ingestion of bismuth salts: clinical and EEG studies of 45 patients

Forty-five patients taking bismuth subnitrate orally for therapeutic reasons were admitted to hospital with a myoclonic encephalopathy of acute onset. The clinical features were similar, mostly with mental confusion, disorder of walking and standing, dysarthria, and myoclonic jerks. In 31 cases the EEG showed a characteristic pattern, not previously recognised, which assisted differential diagnosis.