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Myoclonus
1. MYOCLONUS
Dr PS Deb MD, DM
Director Neurology
GNRC Hospitals ,
Guwahati,
Assam, India
2. MYOCLONUS
Definition
Sudden shock like contraction of muscle.
Flexor of upper limb and extensor of lower limb
Varying in severity from insufficient to move the joints to fall in
ground
Sensory stimulation aggravate attack.
EMG
Burst of 30-60 ms synchronous
Burst of 75-125 ms asynchronous
Burst of >150 ms synchronous
C-reflex – Stimulation of nerve → time locked response.
EEG
Variable pattern
Time lag with EMG activity before or after
Back averaging required
3. FOCAL MYOCLONUS
Rhythmic, unchanged by rest, action, sleep,
walking due to generation of discharge from
discrete segment of neuraxis.
Segmental myoclonus when segment of neuraxis
involved. Arrhythmic.
Spontaneous / Action / intentional / reflex
Cortical
Usually multifocal
Distal > proximal, flexor > extensor
Intentional or reflex , may be modality specific
4. EPILEPSIA PARTIALIS CONTINUA
Rhythmic form, Group of muscles – face, arm or leg,
persist for months
Etiology – vascular, trauma, infection, MS, tumor
EMG: Burst of agonist muscles, synchronous with
antagonistic muscle
EEG – Focal positive negative transient over sensory-
motor cortex contralateral to the jerk, time locked 20sec.
C-Reflex – correlated with giant somato-sensory evoked
potential
Evoked potential – large component of P1N2 has some
relation to C-reflex as the positive negative transient to
the spontaneous jerk
Cranial nerve involvement cephalocaudal
5. CORTICAL MYOCLONUS
Mechanism
Hyper excitability of the sensory-motor cortex → large
synchronous discharge → muscle jerk
Paroxysmal depolarization shift (fragment of epilepsy)
Cause
Any focal cortical damage
Tumor,
Angioma
Encephalitis
Idiopathic
Treatment
Surgical removal of the cause
Anticonvulsant
6. BRAINSTEM MYOCLONUS: PALATAL
MYOCLONUS
Clinical
Rhythmic oscillation of palate sometime other part
(ocular, tongue, larynx, pharynx, diaphragm)
Brachial muscles are affected related to rhythmicity of
respiration/gill movement
Persist during sleep -1.5-3Hz
Mechanism:
Tegmental tract lesion → Inf. Olive oscillate → Purkunji
cell → Reticulospinal tract / vestibulospinal tract
Any lesion of Gullain Mollaret Triangle – Dentate – Red
nucleus – Inf. Olive
Pathology
Hypertrophic degeneration of inf. Olive.
7. PALATAL MYOCLONUS CONT…
Cause
Idiopathic
Stroke
Trauma
Tumor → 10months later
Metabolic encephalopathy
Prognosis: Resistant
Treatment
Tetrabenazine
Halloparidol
5-Hydroxytryptophan
Carbamazipine
Bulbar myoclonus: Tongue and neck movement
8. SPINAL MYOCLONUS
Clinical
Rhythmic > arrhythmic
Spontaneous, persist in sleep
One limb, adjacent trunk or both legs
Cause
Degenerative
Demylination
C. myelopathy
Tumor,
Following spinal anesthesia
Contrast injection
Rarely idiopathic
Ischemic myelopathy : stimulus sensitive myoclonus
Rx: Clonazepam
9. PERIPHERAL MYOCLONUS
Rarely true myoclonus is seen with acute or chronic
denervation in involved muscle
Lesion:
Nerve
Brachial plexus
Nerve root
Essential – rarely focal
Treatment: Clonazepam
10. MULTIFOCAL OR GENERALIZED (EPILEPTIC
MYOCLONUS)
Types
Multifocal : focal jerks at different part of body
Generalized: Large part of body affected
Etiology may be same
Cortical:
Increased excitability of brain due to paroxysmal
depolarization shift involving group of neuron in different
part of brain – Fragment of epilepsy
EEG shows typical multifocal discharge and cortical
correlation
SSEP - ↑
11. RETICULAR – GENERALIZED
Clinical
Proximal more than distal
Flexor more than extensor
Sometime segment of body all muscle
Spontaneous or reflex or action
Cranial muscle → caudo-cephalic involvement
Mechanism
Hyper-excitability of a portion of the caudal brain stem reticular
formation – the nucleus reticularis gigentocellularis
EEG:
Spike, generalized highest amplitude vertex
Follow the EMG burst of myoclonus
Spike is not time locked to the myoclonus, spike is projected and
not directly responsible for myoclonus
SEP is not enhance (no cortical hyperactivity)
Combined Reticular and Cortical myoclonus due to combined
lesion
12. PRIMARY GENERALIZED EPILEPTIC
MYOCLONUS
Focal
Commonly small focal movement with finger movement
(minipolymyoclonus also seen with peripheral denervation)
Generalized
Synchronized whole body jerk (fragment of gen. epilepsy)
Cranial muscle activation down the brain stem
Mechanism
Whole cortex is hyper excitable and is driven to a paroxysm
by normal ascending impulse from the brain stem reticular
formation and non specific thalamic nuclei.
Ascending impulse could be paroxysmal
EEG:
Generalized fronto central predominance, slow negativity
which precedes the myoclonus
For small jerk this event last 100-250 ms and jitter in time with
respect to jerk
13. PROGRESSIVE MYOCLONIC EPILEPSY
Nonspecific, various condition with progressive multifocal or
generalized epilepsy ± dementia
1. Spinocerebellar Degeneration
Clinical
Heterogenous syndrome (Prototype : Mitochondrial myopathy,
Hexose aminidase A deficiency)
Progressive myoclonus Reflex + action
Generalized epilepsy
Cerebellar ataxia
Sporadic or AR
Onset 5-15 years
Occasional associated
Dementia
Spasticity
Myopathy
Neuropathy
Deafness
19. ESSENTIAL MYOCLONUS -
Friedrich – Paramyoclonus multiplex
Myoclonus without seizure, dementia, ataxia
Multifocal or generalized variable magnitude
May present at rest movement or action
No reflex myoclonus
EEG and other lab test should be normal
Familial or sporadic AD, M:F equal
Onset – 1st to 2nd decade
Korten 1974 in a family
Essential myoclonus + tremor
Other member tremor
Both relieved by alcohol
Some cases have dystonia
Balastic movement overflow myoclonus
Treatement: 5HT, VAL, CLZ, Alcohol
20. CHILDHOOD MYOCLONIC EPILEPSIES
Infantile Myoclonus: West syndrome
Benign myoclonic epilepsy of infancy
3-8 months onset
Repetitive flexor spasm
No mental disturbance
Self limiting
Lanox Gastaut syndrome
True myoclonic epilepsy – symptomatic /
cryptogenic
Late Childhood / adolescent –
Myoclonic with absence
Myoclonic epilepsy of adolescent
21. OSCILLATORY MYOCLONUS
Burst of myoclonic jerk which tend to wane in
amplitude
Once started in part of the body the movement may
spread to other part and gradually wane
No other abnormality
Obeso described anoxic injury
22. STARTLE SYNDROME
Clinical
Sudden muscular contraction to surprise stimuli
Onset when start walking
Exaggerated startle → stiffness of body may → fall ± shout
Prominent hypnogogic ± diurnal generalized myoclonic jerks
Hesitant broad based gait
May improve or persist in later life
EMG
response are shorter than normal latency
EEG –
Abrupt onset of spike and slow wave complex maximum from
centrally → background dysynchronization → normal
SSEP –
significant increased amplitude
Hyperactive long latency reflex due to dys-inhibition of certain
brainstem center
May be stimulus sensitive myoclonic disorder
23. STARTLE EPILEPSY
Non habituating startle → tonic extensor spasm →
epilepsy ±
EEG – Desynchornization → frank epileptiform
discharge bilaterally symmetrical or even focal
Jumping/ Latah/ Myriachit – Initial violent startle in
response to sudden unexpected sensory
stimulation → echolalia, echopraxia, coprolalia or
the assumption of defensive posture
24. NOCTURNAL MYOCLONUS
Physiological
Familial nocturnal start
Occur at sleep onset
Gross, generalized body jerk → arousal
Physiological fragmentary myoclonus
Small fragmentary jerk of head face or diffuse
REM sleep or drowsiness
Benign neonatal sleep myoclonus
During all stages of sleep
Lack EEG correlation
No neurological abnormality
25. NOCTURNAL MYOCLONUS
Pathological
Periodic movement in sleep
EEG burst of 200-500ms more than myoclonus
Common in flexor muscle
Periodic 20-30 sec
Two side of the body can be activated independently
Simultaneously or alternating during
NREM sleep or drowsiness
Normally asymptomatic
Baclofen reduces amplitude
26. SLEEP RELATED MOVEMENT DISORDER
Restless leg syndrome
Intense feeling of paresthesia or funny feeling in leg →
desire to move → improve
May be associated with peripheral neuropathy or familial
May be associated with myoclonus or PMS
Clonazepam
Excessive fragmentary myoclonus in NREM sleep
> 50 jerks/ min for 20 consecutive NREM
Associated with other disorder and PMS