3rd Congress of the European Academy of Neurology
Amsterdam, The Netherlands, June 24 – 27, 2017
Hands-on Course 8
MDS-ES/EAN: Neurophysiological study of tremor - Level 1
Orthostatic tremor, cortical tremor, dystonic tremor and psychogenic tremor: Electro-clinical
semiology
Emmanuelle Apartis Paris, France
Email: [email protected]
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Conflict of interest: The author has no conflict of interest in relation to this manuscript.
Key learning objectives
The key learning objectives of the session are to identify the clinical and
electrophysiological core signs of uncommon tremors: orthostatic tremor,
cortical tremor, dystonic tremor and psychogenic tremor, in order to as-
sess an appropriate positive diagnosis and to differentiate them from
other movement disorders, thus leading to adequate care.
Essential knowledge
1. Orthostatic tremor
Primary orthostatic tremor (OT) is a rare disorder that remains under-
diagnosed. OT arises from a central generator located in the posterior
fossa with pathological ponto-cerebello-thalamo-cortical activations 1. OT
predominantly affects women over the age of 50. The cardinal symptoms,
which are highly suggestive of the diagnosis, are feelings of instability, leg
tremor in the standing position, improvement with walking and dis-
appearance while sitting. OT remains mis-diagnosed as vestibular or
cerebellar disorder or psychogenic balance disorder. Yet, the diagnosis of
OT can be very easily assessed by the recording of the typical tremor
activity in the 13-18 Hz range in the legs while standing. This char-
2
acteristic electro-clinical picture differs from those of two looking alike
conditions - tremor in orthostatism and orthostatic myoclonus - frequently
related to neurodegenerative disorders and parkinsonian syndromes.
Signs of OT 2, 3:
- The symptoms appear a few seconds to a few minutes after
standing. They disappear when walking and when sitting at rest.
They are improved when supporting against a wall or a table.
- The major symptom of OT is the feeling of instability, even more
than tremor in the legs. No falls but fear of falling.
- At clinical examination, the tremor is hardly visible, and may be
palpable. The walk and the neurological examination are other-
wise normal.
- Neurophysiology: Very regular tremor of high frequency (13-14
Hz) evidenced in both legs when standing, disappearing at rest and
composed of very short synchronous EMG bursts (20-40 ms). The
higher the tremor amplitude on polymyography, the higher the
disability, both increasing with the duration of standing. Extension
of OT to the trunk and upper limb muscles when standing con-
tinues. High inter-limb and inter-muscular coherence at tremor
frequency.
Signs of tremor in orthostatism:
- Tremor is the major complaint, instability can be mild or absent
- Tremor involves one or two legs when standing
- Tremor is visible at clinical examination
- Tremor can persist when walking or at rest when sitting
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- Neurological examination may be abnormal - rigidity, akinesia,
cerebellar signs -
- Associated conditions : idiopathic Parkinson’s disease, hydroceph-
alus, spino-cerebellar ataxia, brainstem or cerebellar focal lesions,
advanced essential tremor
- Neurophysiology: Regular tremor at slower frequency (3-12 Hz)
than OT, with longer burst duration (70-130 ms) when standing.
Associated proximal or distal rest tremor in the lower limb at the
same frequency. Possibly, re-emergent parkinsonian tremor of the
lower limbs, with posture or when standing.
Signs of orthostatic myoclonus 4:
- Similar symptoms than OT, with frequent feeling of instability,
sometimes feeling of “ shaky-legs”, more than tremor.
- Persistence at walk, fear of falling and falls
- Neurological examination is frequently abnormal – rigidity, akine-
sia, cerebellar signs, cognitive signs
- Associated conditions: mainly idiopathic Parkinson’s disease, also
Lewy body dementia, Alzheimer’s disease, multiple system atro-
phy, progressive supra-nuclear palsy
- Neurophysiology: Irregular myoclonic bursts, in the lower limbs,
asynchronous, bursts duration (40 to 100 ms), frequency range (6-
11 per seconds), occurring predominantly when standing, some-
times persisting at walk or with outstretched legs. No inter-limb
coherence at a given frequency. The generator may be either
cortical or sub-cortical, depending on the underlying disease.
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2. Cortical tremor 5,6
Familial Cortical Myoclonic Tremor (FCMT) is a rare condition with an
action tremor to be distinguished from essential tremor, considering the
different therapeutic issues for both diseases. FCMT is an autosomal
dominant disease characterized by a slow or non-progressive adult-onset,
involuntary repetitive myoclonic jerks of the distal upper limbs, looking
like an irregular tremor enhanced by outstretched posture and action.
Progressive myoclonic epilepsy is excluded by the absence of ataxia and
mental retardation and by the benign course of the disease. In this back-
ground, the association of an upper limb postural tremor with generalized
epilepsia or a familial history of epilepsia, and its resistance to beta-
blockers should question this diagnosis, considering the good response of
FCMT to anti-epileptic drugs. Focal cortical tremor may also occur with
congenital or acquired lesions of the cortical fronto-central area. Electro-
physiological findings in FCMT and focal cortical tremor fulfil criteria for
cortical myoclonus.
Neurophysiology of FCMT:
- Irregular postural tremor recorded on the accelerometer (5-10 per
second)
- Brief polymyographic bursts lasting less than 50 ms in the distal
muscles
- Predominant at postural maintenance, absent at rest, not en-
hanced with intention
- Neurophysiological signs of cortical hyperexcitability and evidence
for a cortical generator of the myoclonus:
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o Giant cortical components of somato-sensory evoked po-
tentials (P25-N33>10 µV)
o Enhanced long-loop transcortical C-reflex (latency: 45-50 ms)
o Cortical focal transients preceding myoclonic jerks by 10-
25 ms, demonstrable by the EEG jerk-locked back aver-
aging method.
3. Dystonic tremor 7
Dystonic tremor is classically defined as tremor in a body part that is
affected by dystonia. Tremor is a common feature in patients with adult-
onset focal dystonia and may involve several different body parts - i.e.
cervical dystonic tremor, upper limb dystonic tremor, truncal tremor -.
Dystonic features may be severe but also mild. Dystonic tremor may also
be isolated, without overt clinical signs of dystonia 8. Dystonic tremor
should be distinguished from tremor that is associated with dystonia, i.e.,
that occurs in a body part not affected by dystonia. In addition to its
diagnosis value, neurophysiological recording can be helpful in assessing
the more active muscles and guiding the botulinum toxin injections when
dystonic tremor is highly focal;
Classical signs of dystonic tremor:
- Typically, postural or action tremor, rarely manifesting at rest
- Suppression by sensory tricks (“geste antagoniste”)
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- Clinical dystonic features in the same body part
o Abnormal posture
o Motor overflow defined as unintentional muscle contrac-
tion, affecting the electivity of a voluntary movement
- Tremor elicited by a specific task or a selective position of the
body part
- Neurophysiology:
o Irregular tremor, with variable duration (50-300 ms) and
amplitude of consecutive bursts
o Variable frequencies (3-12 Hz)
o Sustained contractions, spasms or myoclonus associated to
tremor
o Co-contraction of agonistic and antagonistic muscles (i.e.
wrist flexors and wrist extensors)
Special features of cervical dystonic tremor 9:
- In addition to the criteria mentioned above,
- Recording of the neck muscles allows comparing the activities of
the coupled muscles that rotate the head to the left - left splenius
and right sterno-cleido-mastoideus - to those that rotate the head
to the right - right splenius and left sterno-cleido-mastoideus - .
- An asymmetrical location of the tremor in rotator muscles or
elective involvement of one couple argues for dystonic cervical
tremor and against essential cervical tremor.
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Signs of pure writing tremor:
- Regular or irregular tremor occurring specifically with writing
- Disappearance of tremor during postural maintenance, during non-
specific actions and other tasks than writing
- Mirror writing tremor elicited at rest by writing with the contra-
lateral hand
- Lack of overt dystonic features in the affected hand
3. Psychogenic tremor
Psychogenic tremor frequently involves the upper limbs, but may affect
every part in the body including neck, legs and trunk. It may occur
under different conditions, rest, posture, action, intention, and even
with orthostatism. After evidence of the clinical clues suggestive of
psychogenic tremor, neurophysiological tools are necessary to assess the
diagnosis by revealing objective positive signs in comparison to the
classical characteristics of tremors of organic origin. Psychogenic tremor
should be distinguished chiefly from pyramidal clonus and organic tremors
such as enhanced physiologic tremor, parkinsonian tremor, dystonic trem-
or, and odd tremors. In some cases, these physiological data combined
with the patient insight during the tests, are beneficial in persuading the
patients of the accuracy of the diagnosis and of the potential reversibility
of their symptoms.
Clinical clues for psychogenic tremor:
- Tremor with a sudden onset
- Tremor with a variable course, periods of complete normality
- Distractibility
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- Fluctuations of intensity, or sudden shifts of the localization or
the axis of tremor, particularly if they are provoked by external
manipulations (i.e., passive immobilization of the hand inducing
the shifting of tremor to the shoulder or to another body part)
- Inconsistencies
Neurophysiological signs of psychogenic tremor 10,11:
Among criteria listed by R Helmich (part 1 of the HoC: Neurophysiological
study of tremor: how to do it in clinical practice), the strongest are
related to the tremor frequency analysis and manipulation by the
examiner:
- The spontaneous variability of tremor frequency
- The frequency driving induced by contralateral rhythmic tasks,
By contrast, organic tremors have a stable frequency that cannot be
driven to another one. Tips and tricks adapted to the body part affected
by the psychogenic tremor, and pitfalls in tremor variability assessment
and interpretation will be highlighted, with a special attention paid to the
differential diagnosis of dystonic tremor.
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References and suggested reading:
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cerebello-thalamo-cortical activations in primary orthostatic
tremor during lying and stance. Brain. 2017 Jan;140:83-97.
2. Ganos C, Maugest L, Apartis E, Gasca-Salas C, Cáceres-Redondo MT,
Erro R, Navalpotro-Gómez I, Batla A, Antelmi E, Degos B, Roze E,
Welter ML, Mestre T, Palomar FJ, Isayama R, Chen R, Cordivari C,
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Wilkinson JR. Orthostatic tremor: Clinical, electrophysiologic,
and treatment findings in 184 patients. Neurology. 2016 Feb
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4. Gasca-Salas C, Arcocha J, Artieda J, Pastor P. Orthostatic
myoclonus: an underrecognized cause of unsteadiness?
Parkinsonism Relat Disord. 2013 Nov;19(11):1013-7.
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Cortical tremor: a variant of cortical reflex myoclonus.
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7. Defazio G, Conte A, Gigante AF, Fabbrini G, Berardelli A.
Is tremor in dystonia a phenotypic feature of dystonia?
Neurology. 2015 Mar 10;84(10):1053-9. Review.
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an update. Curr Opin Neurol. 2015;28(4):393-9.
9. Deuschl G, Heinen F, Kleedorfer B, Wagner M, Lücking CH,
Poewe W. Clinical and polymyographic investigation of
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