Differences in gait apraxia due to reduced regional cerebral blood flow in the supplementary motor area in corticobasal syndrome: a report of two cases.

backgroundGait apraxia, characterized by difficulties initiating and coordinating walking despite preserved conceptual movement abilities, is a distinct entity from lower limb apraxia. Although gait apraxia has been associated with dysfunction of the frontal lobe, particularly the supplementary motor area (SMA), the specific associated somatotopic organization phenotype remains poorly understood. Corticobasal syndrome (CBS), a clinical phenotype of corticobasal degeneration, commonly presents with upper limb apraxia, while lower limb or gait apraxia has rarely been reported. Herein, we describe two rare cases of CBS presenting with gait apraxia shown to be caused by SMA dysfunction, based on regional cerebral blood flow (rCBF) reduction on single-photon emission computed tomography (SPECT). CASE PRESENTATION: Case 1 was of an 82-year-old man who exhibited right-sided apraxic gait with freezing and shuffling patterns, along with SMA hypoperfusion in both the dorsal and pre-SMA regions. Neurological examination revealed mild rigidity, right-sided Babinski sign, and clumsiness in mimicking leg movements. Gait patterns were inconsistent and unresponsive to levodopa treatment or sensory cues. Case 2 was of an 80-year-old man who demonstrated a peculiar gait characterized by exaggerated right leg movements and everted ankle positioning. Hypoperfusion was localized to the left dorsal SMA. Examination findings included rigidity and impaired hand weight perception. Sensory tricks and levodopa provided no benefit.

conclusionThese cases highlight the role of SMA dysfunction in the pathogenesis of gait apraxia. Variations in rCBF reduction correlated with distinct gait patterns. For example, the freezing gait shown in Case 1 likely resulted from pre-SMA impairment, which is critical for movement initiation, while the exaggerated leg movements in Case 2 reflected dorsal SMA dysfunction, involved in motor execution. These results indicate that gait apraxia, which is often underdiagnosed, should be recognized as a potential early indicator of CBS. Further, these cases suggest that SMA dysfunction, identified through SPECT imaging, underlies the distinct gait patterns seen in CBS patients with apraxic gait. Recognizing these symptoms, even in the absence of weakness or limb apraxia, may aid in early CBS diagnosis and improve clinical management.