A SPECT study of patients with gait apraxia without evidence of frontal lobe dysfunction

The pathogenesis of gait apraxia (GA) is unknown. Even though imaging studies provide excellent assessment of brain morphology, there is still a lack of congruous results. Single photon emission computed tomography (SPECT) using Tc-99m hexamethylpropyleneamine oxime (HMPAO) may show alterations in regional cerebral blood flow (rCBF) and provide indirect information about brain metabolism.

We conducted a SPECT study of GA patients and evaluated the related cortical function. rCBF was assessed in 16 GA patients (15 male, one female; age range 65-79 years, mean 70.5 years) by SPECT using HMPAO. Mean HMPAO cortical or basal ganglia/cerebellum activity ratios were calculated. The regions of interest included the frontal lobe, parietal lobe and basal ganglia. A battery of GA tests and magnetic resonance imaging (MRI) of the brain were also performed in these 16 patients.

Nine of the patients had equilibrium disorder, and all 16 patients had locomotion disorder. The MRI findings were lacunar infarct (16/16 in basal ganglia, or 6/16 in thalamus), leukoaraiosis (4/16), enlarged ventricle (3/16), frontal lesion (3/16) and parietal lesion (1/16). Lower rCBF was noted in the frontal lobe (3/16), occipital lobe (1/16, thalamus (7/16) and basal ganglia (9/16). Though SPECT showed decreased rCBF in nine patients (9/16), mean cortical and basal ganglia regional uptake ratios in the patient group were not significantly different from values in the control group (cortical p = 0.0613; basal ganglia p = 0.0576, by Student's t-test).

Though only a small number of patients were studied, it was clear that brain SPECT and MRI did not show any significant abnormalities in the frontal or parietal lobes of patients with GA. Thus, the pathogenesis of GA and its related anatomic lesion should be further investigated.