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|
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.
- 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.
- 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.