Tremor

INDEX

ORIGIN

The tremor is believed to have a cerebellar generator, acting as a single oscillator that creates a similar intermuscular coherent tremor in all affected limbs.

CLASSIFICATION

This is preliminary. OT may be divided into primary, presenting typically around the age of 50, and secondary, associated with other neurodegenerative diseases, slow, and OT-plus

Secondary or symptomatic causes include: aqueduct stenosis, pontine and midbrain lesions, tardive (following exposure to dopamine blocking drugs), cerebellar degeneration, spinal-cord lesions, stiff person syndrome, multiple sclerosis, vitamin B12 deficiency and head trauma.

"Slow OT" has a tremor frequency < 13 Hz, and has been associated with MS, PD and ET.

OT-plus is the name given to OT when co-occurring with other primary neurological disorders and is seen with restless leg syndrome, orobuccal dyskinesias of uncertain aetiology, cerebellar ataxia, progressive supranuclear palsy and PD.

CLINICAL FEATURES

OT is characterized by the presence of a high-frequency tremor (>13 Hz) in the legs that occurs or increases upon standing.  Patients may report that they avoid situations in which they must stand still for long periods such as taking a shower or waiting in line. Tremor is absent at rest. Patients usually complain of a feeling of unsteadiness when standing, which is relieved by walking and sitting down, and do not mention tremor.  Often the feeling of unsteadiness is reduced by standing with a widened stance and clawing the floor with the toes. Tremor is a fine amplitude rippling of upper leg muscles, sometimes with knee tremor. Tremor may not be visible when examining the leg muscles, whereas a postural arm tremor may be visible. With a stethoscope, the fast beating “helicopter sign" can often be heard, and fast tremor may be palpated. A proportion of patients may progress. Duration of symptoms before diagnosis is typically 5 years or more.

AGE OF ONSET

Typically around 60 years, but range is 13-85 years.

DISTRIBUTION

Head 20%; Tongue 7%; Voice 7%, Trunk.

DIAGNOSIS

EMG or accelerometry of quadriceps or gastrocnemius. The frequency of arm tremor is lower: 5-10 Hz. Little effect from alcohol.

DIFFERENTIAL DIAGNOSIS

Orthostatic myoclonus: characterized by myoclonus in multiple leg muscles that appeared or increased

Immediately upon standing; frequency of the jerks was from 5-12 Hz.

PD: medium-slow leg tremor (4-6 Hz)

DIAGNOSTIC TESTS

Auscultation, EMG recording of tremor frequency from quadriceps muscles.

TREATMENT

Frequently highly unsatisfactory.

Clonazepam (0.5 -2 mg tds)

Gabapentin (300- 2400 mg daily)

Primidone and levodopa and dopamine agonists have been tried. Little response to propranolol or alcohol. Physical aids may be of benefit. Patients may consult: https://www.orthostatictremor.org/

REFERENCES

Jones L, Bain PG. Orthostatic tremor. Pract Neurol. 2011; 11(4):240-3.