The spectrum of disorders presenting as adult-onset focal lower extremity dystonia.

BACKGROUND

Uncommonly, adult-onset dystonia is confined to one lower extremity. We sought to characterize the clinical spectrum associated with the presenting phenotype of lower limb dystonia including foot torsion.

METHODS

Retrospective computer search of the Mayo Clinic Medical Records Linkage System (1996-2006). Inclusion criteria were (1) a principal, initial diagnosis of monomelic lower extremity dystonia with foot torsion; (2) no neurologic findings outside of the affected limb; (3) age-onset>18 years. Prospective data were sought from apparent idiopathic cases.

RESULTS

We identified 36 patients (31 females) presenting with monomelic lower limb dystonia including foot torsion. Onset was usually subacute or insidious (32 patients); mean symptom duration was 28.8 months (range, 1-96), age-onset 47.5 years (range, 21-77). After a mean follow-up of 3.1 years, causes were identified in over half, including 5 with parkinsonism. Other treatable etiologies included psychogenic dystonia (3 patients) and stiff-limb syndrome (2 patients). Post-traumatic dystonia was diagnosed in 10 patients and consistently manifested as fixed, painful foot torsion, in contrast to the action-induced dystonia in 5 parkinsonism cases, and 10 of 14 patients with primary lower limb dystonia. Imaging identified the cause in only 1 patient (ischemic stroke) and was negative in the single patient with pyramidal signs.

CONCLUSIONS

Adults presenting with monomelic lower limb dystonia with foot torsion often have an identifiable cause, sometimes treatable, including Parkinson's disease (diagnosed with levodopa trial) or immune-mediated stiff-limb syndrome. Post-traumatic dystonia was the single most frequent cause and proved difficult to treat. Unlike certain other series of such patients, psychogenic dystonia was an uncommon clinical diagnosis.