Abnormal Movements
Differential Diagnosis
Common Diagnoses
- RLS
- Myokymia (Affecting Orbicularis Oculi Muscles)
- Drug Induced: Including Choreoathetosis, Dystonias, Tardive Dyskinesias and Akathisia (Drugs Include L-Dopa, Tricyclic Antidepressants, Metoclopramide and Antipsychotics)
- Tourette’s
- Simple Partial Seizures
Occasional Diagnoses
- Anxiety/Nervous TIC (Common, but Rarely Presented to the GP)
- Muscle Fasciculation (e.g. Benign Fasciculation, Motor Neurone Disease)
- Simple Childhood Tics (Common, but Infrequently Presented)
- Dystonias
- Periodic Leg Movements During Sleep
Rare Diagnoses
- Hemifacial Spasm
- Myoclonus
- Chorea (Sydenham’s, Huntington’s)
- Wilson’s Disease
- Hemiballismus (e.g. Post Stroke)
- Hysterical
Ready Reckoner
Key distinguishing features of the most common diagnoses
| RLS | Myokymia | Drug Induced | Tourette’s | Simple Partial Seizures | |
|---|---|---|---|---|---|
| Worse at Rest | Yes | Possible | No | No | No |
| Patient on Medication | Possible | Possible | Yes | Possible | Possible |
| Whole Limb Affected | Yes | No | Possible | Possible | Possible |
| Other Neurological Signs | No | No | No | No | Possible |
| Childhood Onset | No | No | Possible | Yes | Possible |
Possible Investigations
Likely:FBC, U&E, ferritin, B12, folate, TFT, fasting glucose or HbA1c, calcium.
Possible:CT/MRI of brain or spinal cord, EEG, EMG, nerve conduction studies.
Small Print:Other specialised tests (e.g. for myoclonus and Huntington’s).
- FBC, ferritin: To assess for iron deficiency in RLS.
- U&E: Renal failure is a potential cause of RLS and can be implicated in partial seizures.
- B12, folate: Deficiencies may cause or mimic RLS.
- TFT: Hypothyroidism may cause RLS.
- Fasting glucose or HbA1c: Diabetes may cause RLS or partial seizures.
- Calcium: Hypocalcaemia may be implicated in seizures.
- CT/MRI of brain or spinal cord: May be required in investigation of fasciculation and seizures (usually arranged after specialist referral).
- EEG: For investigation of seizures.
- Other specialised tests: Usually arranged by neurologist to explore the more obscure diagnoses such as Huntington’s chorea and Wilson’s disease.
Top Tips
- When faced with odd and otherwise inexplicable movements of recent onset in a patient, remember to take a drug history.
- Bear in mind that abnormal movements can be caused by a drug that the patient has been taking for some time (e.g. tardive dyskinesias).
- Patients with myokymia sometimes become disproportionately anxious about the symptom, imagining all sorts of possible neurological catastrophes – they may need a lot of reassurance.
Red Flags
- Childhood tics tend to be single; the patient with the much more significant Tourette’s will probably have multiple tics.
- Drug-induced dystonias may cause odd posturing and require prompt treatment. The diagnosis is easily overlooked – antipsychotics are common culprits, so it is easy to erroneously attribute the dystonia to psychiatric pathology.
- Beware of the combination of personality changes and odd movements such as facial grimaces – this could be Huntington’s chorea. Also, don’t be misled by the lack of a positive family history – this background may have been concealed from the patient.