This document discusses myoclonus, which are sudden, involuntary muscle jerks. It describes different types of myoclonus including positive and negative myoclonus. Myoclonus is classified based on distribution, provoking factors, etiology, and presumed origin (cortical, sub-cortical, spinal, peripheral). Evaluation involves examination, electrophysiology to determine origin. Treatment depends on underlying cause but commonly includes valproate, clonazepam, levetiracetam for cortical myoclonus and clonazepam for sub-cortical and spinal myoclonus. Drug treatment is often combined and titrated for optimal effect

1. Myoclonus seizure
Harith Abdulkadir Sheikh

2.  Myoclonus is a sudden, brief, involuntary muscle
jerk.

3.  Positive myoclonus
Is a movement disorder which presents its self
with sudden, brief shock like jerks due to a
brief burst of muscular activity.
 Most common form of Myoclonus.

4.  Negative myoclonus
When jerks result from brief cessation of
ongoing muscular activity.
Occurs mostly in hospital settings, as
result of toxic-metabolic causes.

5. Classification
1: By distribution
- Focal
- Multifocal
- Generalized
2: By provoking factors
- Spontaneous
- Reflex

6. 3: By Etiology
- Physiological (Hypnic Jerk)
- Essential
- Epileptic
- Symptomatic
- Psychogenic

7. Continue ….
4: By presumed source of origin (physiologic)
- Cortical
- Sub-cortical (segmental/non-segmental)
- Spinal
- peripheral
It is most practical way to classify myoclonus , it
guides the physician towards the most effective
treatment.
Drugs that provides the best likelihood of treatment
response in cortical myoclonus are not effective is
segmental myoclonus

8. Cortical myoclonus
 Most common form of myoclonus.
 Affects the distal upper limbs and face (largest
cortical representation).
 Often focal, but can be multifocal or generalized.
 May affect speech and gait

9. Stimulus sensitive typically to touch.
Mostly have both positive and negative
myoclonus.
 if its prolonged and lasts for one hour,
days, weeks it is called Epilepsia Partials
Continua.

10.  Focal cortical myoclonus – originate
from sensori-motor cortex (vascular,
inflamatory, neoplastic).
Multifocal cortical myoclonus – like post
hypoxic myoclonus (Lance-Adams
syndrome)

11. Sub cortical myoclonus
 Sub cortical myoclonus has its origin between
cortex and the spinal cord.
 It may divided into:
 segmental
 non segmental

12. Non-segmental Sub cortical
myoclonus
 Its sub divided into
1) Brain stem
- Reticular reflex
- Hyperkplexia
2) Myoclonus dystonia (Hereditary)
3) Drug induced myoclonus (Phenytoin).

13. Brain stem myoclonus
 Generalized jerks
 Most striking clinical feature is sensitivity to
auditory stimuli.
Two types
- Startle/hyperekplexia
- Reticular reflex

14. Hyperekplexia
o Startle : defensive posture of the body , following an
unexpected stimulus such as sudden noise, it
involves proximal and distal muscles.
o Brief, shock like compromising grimacing
o Arm abduction and flexion of the neck, trunk,
elbows, hips, knees.
o Hyperkplexia is pathological exaggeration of the
normal startle response which doesn’t habituate on
repeated stimuli.
 May be familial , idiopathic, result from brain stem
encephalitis or multiple sclerosis.

15. Reticular reflex myoclonus
 Generalized myoclonus
 Clinically it may distinguish from hyperkplexia by
the spontaneous myoclonus and sensitivity to
somato-sensory stimuli delivered to distal limbs
rather than to mantle area.
 Occurs in
- Post-hypoxic encephalopathy
- Brain stem encephalitis
- Uremia

16. Spinal myoclonus
 Spinal Myoclonus may be segmental or
propriospinal, reflecting spinal segmental
organization and the presence of propriospinal
pathways which connect different spinal
segments.
 It is generally resistant to supraspinal influences
such as sleep (therefore it may persist in
sleep).

17. Spinal segmental myoclonus
 Usually symptomatic of an underlying structural
lesion such as syringomyelia, myelitis, spinal
cord trauma, vascular lesion or malignancy.
 It is confined to one or few contiguous myotomes.
 EMG myoclonic bursts are prolonged up to
1000ms.

18. Propriospinal myoclonus
 Is a form of spinal myoclonus where the spinal
generator recruits axial muscles up and down the
spinal cord via long propriospinal pathways.
 Typically, there are axial flexion jerks involving
the neck, trunk and hips with a frequency of 1–
6Hz.
 EMG bursts are long, lasting several hundred
milliseconds

19.  Clinically, it can be distinguished from
brainstem myoclonus, which is also axial in
distribution, by sparing of the face and
insensitivity to auditory stimuli.
 It typically occurs spontaneously, especially in
recumbent position or may be provoked by
tapping of the abdomen or by eliciting tendon
reflexes

20. Peripheral myoclonus
Characterized by rhythmic or semirhythmic jerks
secondary to plexus, nerve, root lesion or rarely
anterior horn cell disease.
Hemifacial spasm is the most common example of
peripheral myoclonus.

21. Drugs that may cause myoclonus
o Anticonvulsants (particularly gabapentin, pregabalin,
lamotrigine, phenytoin, phenobarbital).
o Levodopa.
o Antidiarrhoeal bismuth subsalicylate.
o Antidepressants (cyclic antidepressants, selective
serotonin uptake inhibitors, monoamine oxidase inhibitors).
o Anti-infectious agents (quinolone antibiotics,
cephalosporines).
o clozapine, opioids.

22. Approach to patients with myoclonus
On history taking, one should be interested in the
o Age at onset.
o The character of onset (acute versus gradual).
o Precipitating or alleviating factors.
o family history.
o Associated symptoms such as epilepsy, ataxia
and cognitive

23. On examination
oCheck whether myoclonus appears at rest or
during action.
o Note its distribution.
oLook for stimulus sensitivity.
oNeurological signs associated.

24. Neurophysiologic assessment
 Electrophysiology is very helpful to detect
whether myoclonus is cortical, subcortical or
spinal/segmental.
 Polymyography is the first step in the
neurophysiologic assessment of myoclonus and
includes recording of
duration, distribution and stimulus sensitivity
of muscle jerks.
Further investigations include combined EEG–
EMG recording, EEG back averaging and
recording of SSEPs.

25. Cortical myoclonus
 Cortical myoclonus may have the following
electrophysiological characteristics:
(a) It is represented by brief EMG discharges lasting
less than 70ms, usually less than 50ms
(b) An EEG spike precedes the myoclonus by a short
interval (20ms for hand muscles and about 35ms
for the calf muscles);
(c) There is an enhancement of the early cortical
component of the SSEPs, called ‘giant SSEPs’

26.  Conventional EEG–EMG recording, EEG spikes
associated with EMG myoclonic bursts suggest
cortical origin.
 The absence of EEG spikes does not exclude the
possibility of a cortical aetiology

27. Cortical myoclonus EMG and EEG trace
 Cortical myoclonus: EMG and
EEG trace in a case of cortical
myoclonus.
 (A) A magnification of a
segment (20ms/division) where
myoclonic jerks are observed.
 Surface EMG shows brief
bursts of activity (of
approximately 20ms duration)
with a typical rostrocaudal
pattern of muscle activation in
the right upper limb.
 (B) EEG back averaging of the
right first dorsal interossei
muscle.
 EMG burst demonstrates
cortical spikes in C3 derivation,
starting 22ms before the EMG
myoclonic burst.

28. Subcortical myoclonus
 In contrast with cortical myoclonus, in subcortical
myoclonus there are no signs of
hyperexcitability on the EEG and SSEP
recordings.

29. Brainstem myoclonus EMG
 Simultaneous recording of surface EMG
(multichannel surface EMG) from different
muscles may give information on the distribution
and mode of spread of myoclonus in the case of
brainstem myoclonus.
 The first activated muscle is
sternocleidomastoid or trapezius with
subsequent spread of activity to rostral and
caudal muscles.

30. Brainstem reticular myoclonus EMG
 Brainstem reticular
myoclonus.
Multichannel EMG
recording:
 Following acoustic
stimulation there was
an initial activation of
the right
sternocleidomastoid
muscle with a latency
of 68ms, followed by
the spread to rostral
and caudal muscles.

31. Propriospinal myoclonus
 In propriospinal myoclonus, myoclonic bursts may
last from 50ms to 4s.
 EMG jerks arise from abdominal or cervical
spinal segments and spread slowly rostrally and
caudally, sparing the cranial muscles.

32. Propriospinal myoclonus EMG
 Propriospinal myoclonus.
With the patient in a
recumbent position,
surface multichannel
EMG from right-sided
muscles shows a jerk of
approximately 400ms
duration.
 This jerk is electrically
evoked, starts with a
latency of 200ms in the
rectus abdominis
muscle and is followed by
activation of rostral and
caudal muscles.

33. Spinal segmental myoclonus
 In spinal segmental myoclonus, myoclonic
bursts are confined to one or two
contiguous myotomes.

34. Spinal segmental myoclonus EMG
 Spinal segmental
myoclonus.
Multisurface EMG
shows myoclonic
bursts confined mainly
to the right triceps but
affecting also a few
adjacent myotomes.

35. Treatment
 The treatment of myoclonus depends on the
underlying disorder.
 Reversible causes of myoclonus include some
toxic–metabolic states, drug intoxications or
surgically treatable lesions.
 Majority of cases, the underlying cause is not
correctable and symptomatic treatment is the
only possibility.

36.  A useful approach to the treatment is to first
establish the physiology of myoclonus
(cortical versus subcortical or spinal), because
different drugs will work in different types of
myoclonus.
 One single agent can seldom completely control
myoclonus; therefore multiple drug trials and
combination of drugs are necessary, often in
large dosages.

37. Cortical myoclonus
 Sodium valproate is the most effective.
 It should be introduced slowly and titrated up to
1200–2000mg daily.
 Clonazepam in large doses (up to 15mg a day).
Tolerance may develop after several months.
 levetiracetam 3000mg daily.
 Primidone and phenobarbital are rarely effective.

38. Phenytoin, carbamazepine, lamotrigine and
vigabatrin are
best avoided in cortical myoclonus, as they
may paradoxically exacerbate myoclonus.

39. Subcortical myoclonus
 Antiepileptic drugs used in cortical myoclonus are
not effective in subcortical myoclonus.
 Clonazepam is useful in hyperekplexia and
partially in reticular reflex myoclonus

40. Spinal myoclonus
 In spinal myoclonus, pharmacological treatment is
unsatisfactory.
 Clonazepam is the drug of first choice for both
types of spinal myoclonus.
 Levetiracetam was reported to be effective.

41. Peripheral myoclonus
 Drugs are usually ineffective.
 carbamazepine may have some effect.
 Hemifacial spasm responds excellently to
botulinum toxin injections

42. Reference
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC303
6960/
(Myoclonic disorders: a practical approach for
diagnosis and treatment)

43. Thanks