Myoclonus

Dr. Sachin Adukia

Myoclonus is a clinical sign that is characterized by brief, shocklike, involuntary movements caused by muscular contractions or inhibitions [1].

Muscular contractions produce positive myoclonus,

muscular inhibitions produce negative myoclonus (ie, asterixis).

Patients will usually describe myoclonus as consisting of "jerks," "shakes," or "spasms."

ANATOMIC AND PHYSIOLOGIC CLASSIFICATION

classified by the localization of the physiologic mechanism that generates it Cortical Cortical-subcortical Subcortical-nonsegmental Segmental Peripheral

Cortical

focal discharge from the primary sensorimotor cortex causes

myoclonic jerk

Occurs because of insufficient inhibition within neuronal circuits

of the primary motor cortex, primary sensory cortex, or both

Rapid generalization - can produce myoclonic seizures in certain

epileptic syndromes

may occur with reflex sensory stimulation (cortical reflex myoclonus), Muscle activation (cortical action myoclonus), with rest (eg, focal motor seizure), or any combination

Cortical-subcortical

involves abnormal, paroxysmal, and excessive oscillation in bidirectional connections between cortical and subcortical sites.

is the major mechanism for myoclonic seizures in primary generalized epileptic syndromes (JME) and others (eg, minipolymyoclonus).

Eg: in JME and absence epilepsy, thalamic networks abnormally couple with widespread cortical areas to produce excessive neuronal activity

The resulting myoclonic jerks are commonly generalized or bisynchronous.

Subcortical-nonsegmental

myoclonus is generated from a site that is subcortical, but myoclonus manifests far beyond segments that are near the originating site.

Eg. reticular-reflex myoclonus and propriospinalabnormal activity begins in a focal area of neuraxis

and then spreads in both rostral and caudal directions, producing generalized myoclonus

Segmental myoclonus

generated at a particular segment or contiguous segments of brainstem and/or spinal cord.

Freq. of motor oscillations < tremor.manifests at, or close to, that particular segment or

contiguous segments of the body palatal myoclonus spinal segmental myoclonus

Peripheral myoclonus

arises d/t peripheral nervous system lesionproduces hyperactive motor discharges to its

muscle (eg, hemifacial spasm).

Anatomic and physiologic classification

CLINICAL AND ETIOLOGIC CLASSIFICATION

classification scheme of Marsden and colleagues● Physiologic● Essential● Epileptic● Secondary (symptomatic)

Physiological: Jerks associated with sleep

occur during sleep or sleep transitions Partial myoclonic jerks – multifocal, s/i distal muscles Massive myoclonic jerks – hypnic- gen., affect trunk and

proximal muscles Periodic movements of sleep (nocturnal myoclonus) are

stereotyped repetitive dorsiflexion of toes and feet, sometimes with flexion of knees and hips

Essential myoclonus-divided into sporadic and hereditary

myoclonus is the most prominent or only clinical finding - ie, an "essential" phenomenon

Sporadic (or idiopathic) essential myoclonus - heterogeneous w.r.t. distribution, exacerbating factors, CNS findings Palatal myoclonus

often 2o to brainstem and/or cerebellar lesion. However, some patients have no apparent structural lesion -

essential palatal myoclonus. myoclonus is c/b contractions of the tensor veli palatini

secondary (symptomatic) c/b contractions of levator veli palatini.

Hereditary essential myoclonus

demonstrates a subcortical-nonsegmental physiology Clinical features

Onset < 20 yrs AD benign course - active life and normal lifespan Absence of cerebellar ataxia, spasticity, dementia, and seizures

occurs throughout arms & axial muscles. exacerbated by muscle activation markedly diminished with alcohol ingestion.

Epileptic myoclonus

Is myoclonus in the setting of epilepsy cortical or cortical-subcortical physiologySeizures dominate the clinical pictureidiopathic, genetic, or a static encephalopathyMyoclonus can occur as

one of several components of a seizure the only seizure manifestation - myoclonic seizure one of multiple seizure types within an epileptic

syndrome

Familial cortical myoclonic tremor with epilepsy

Autosomal dominant inheritance Adult onset Distal action tremor and myoclonus Infrequent, 2o GTCS Relatively benign course, typically normal cognition Responsiveness to anticonvulsants

Symptomatic (secondary) myoclonus

occurs as a secondary symptom of neurologic or non-neurologic disorder

Part three

Treatment

to control myoclonus - treat the underlying disorder may reverse certain myoclonus

myoclonus caused by an acquired abnormal metabolic state medication or toxin excisable lesion psychogenic etiology

Evidence base for treatment is mainly of observational case series and case reports

Cortical myoclonus

Drug treatment – aim is to augment inhibitory processes within sensorimotor cortex

Levetiracetam, piracetam- initial drugs clonazepam and valproic acid – add on’sGait disturbance - most resistant to treatment. An unsteady gait with frequent falls may persist despite

control of action and reflex myoclonus in ULAlso, there is no consistent evidence for benefit in

negative myoclonus (asterixis).

Cortical-subcortical myoclonus

Includes the myoclonus in PGETreatment is that of epilepsy

Subcortical-nonsegmental myoclonus

Standard antiepileptic treatments- not helpfulIn addition, increased risk of alcoholism in patients with

essential myoclonus (including myoclonus-dystonia) because condition is ethanol-responsive.

initial treatment with clonazepamBenztropine or trihexyphenidyl – alternatives for initial

or add-on therapy in essential myoclonus, including myoclonus-dystonia

Zonisamide- propriospinal myoclonus.

Segmental myoclonus

Spinal Myoclonus clonazepam (up to 6 mg daily) However, benefit - limited. Alternatives- levetiracetam, botulinum toxin injection,

carbamazepine, diazepam, and tetrabenazine. Palatal myoclonus –

botulinum toxin injections as initial treatment for debilitating palatal myoclonus

pharmacologic interventions- no benefit possibly useful drugs :

clonazepam, piracetam, valproic acid, baclofen, carbamazepine, lamotrigine, phenytoin, sumatriptan, and tetrabenazine.

Peripheral myoclonus

botulinum toxin injection hemifacial spasm and other peripheral myoclonus

carbamazepine may have some effect.

Thank You