Freezing of gait and postural instability: the unpredictable response to levodopa in Parkinson's disease

Freezing of gait (FOG) and postural instability are challenging motor symptoms that present a serious therapeutic dilemma in Parkinson's disease. Appropriate distinction between FOG subtypes may be difficult during routine clinical visits, as shown in the case we present. The patient was examined in three different states in relation to levodopa (L-DOPA) and apomorphine subcutaneous (sc) tests with video documentation: (1) 'overnight-off', after 12 hours without medication; (2)'on', 60 min after intake of regular levodopa dose (200 mg) and 20 min after 2 mg of apomorphine sc; and (3) 'supra-on', after 350 mg of L-DOPA and 3 mg of apomorphine sc. The patient clearly showed a dose-dependent paradoxical response to L-DOPA treatment with the emergence of severe FOG and postural instability. The tendency to develop these axial symptoms was less pronounced with apomorphine at doses that achieved similar improvements of other Parkinsonian features.