Differentials
Tic disorder
SIGNS / SYMPTOMS
Patterned, repetitive movements that may be associated with premonitory urge. Tics are usually suppressible.
INVESTIGATIONS
Clinical diagnosis: the diagnosis is made on the basis of the history and a normal physical examination.
Levodopa-induced dyskinesia
SIGNS / SYMPTOMS
A history of long-term intake of levodopa for treatment of Parkinson's disease.
INVESTIGATIONS
Clinical diagnosis.
Drug-induced parkinsonism
SIGNS / SYMPTOMS
Symmetrical symptoms.
Slowness of movement (bradykinesia), shuffling gait, and possible hand tremor.
INVESTIGATIONS
Clinical diagnosis.
Dystonia
SIGNS / SYMPTOMS
Muscle pain, dystonia worsens with action. May involve hands and feet.
INVESTIGATIONS
Levodopa responsiveness: positive.
Cranial MRI (if an acquired cause is suspected): normal.
GCH1 gene testing (in some cases to confirm the presence of some causes of dopa-responsive dystonia): variable; GCH1 gene mutations usually result in a single amino acid change in the GTP cyclohydrolase 1 enzyme.
Huntington's disease
SIGNS / SYMPTOMS
Patients with Huntington's disease usually have upper facial involvement (forehead chorea). Chorea is more generalised, and patients usually have cognitive dysfunction and behavioural abnormalities. Patients may have a positive family history of Huntington's disease.
INVESTIGATIONS
HTT mutation testing (CAG repeat testing): a positive result for Huntington's disease is ≥40 CAG repeats on 1 of the 2 alleles; an intermediate result is 36 to 39 repeats.
MRI brain: striatal atrophy.
CT may be performed if MRI is unavailable.
Stroke
SIGNS / SYMPTOMS
Acute onset of involuntary, asymmetric movements in the face and other body parts.
INVESTIGATIONS
Clinical diagnosis: CT may be normal, or may show signs of infarction or haemorrhage.
Severe hyperglycaemia
SIGNS / SYMPTOMS
Acute or subacute onset of involuntary movements in face or extremities in patients with diabetes mellitus.
INVESTIGATIONS
Blood glucose and HbA1c: elevated. There is no cut-off value at which hyperglycaemia causes involuntary movements. In one study of patients with diabetic striatopathy, the average blood glucose and HbA1c level was 22.98 mmol/L (414 mg/dL) and 13.1%, respectively.[37]
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