Abstract
Both the supplementary motor complex (SMC), consisting of the supplementary motor area (SMA) proper, the pre-SMA, and the supplementary eye field, and the rostral cingulate cortex are supplied by the anterior cerebral artery (ACA) and are involved in higher motor control. The Bereitschaftspotential (BP) originates from the SMC and reflects cognitive preparation processes before volitional movements. ACA strokes may lead to impaired motor control in the absence of limb weakness and evoke an alien hand syndrome (AHS) in its extreme form. To characterize the clinical spectrum of disturbed motor control after ACA strokes, including signs attributable to AHS and to identify the underlying neuroanatomical correlates. A clinical assessment focusing on signs of disturbed motor control including intermanual conflict (i.e., bilateral hand movements directed at opposite purposes), lack of self-initiated movements, exaggerated grasping, motor perseverations, mirror movements, and gait apraxia was performed. Symptoms were grouped into (A) AHS-specific and (B) non-AHS-specific signs of upper limbs, and (C) gait apraxia. Lesion summation mapping was applied to the patients' MRI or CT scans to reveal associated lesion patterns. The BP was recorded in two patients. Ten patients with ACA strokes (nine unilateral, one bilateral; mean age: 74.2 years; median NIH-SS at admission: 13.0) were included in this case series. In the acute stage, all cases had marked difficulties to perform volitional hand movements, while movements in response to external stimuli were preserved. In the chronic stage (median follow-up: 83.5 days) initiation of voluntary movements improved, although all patients showed persistent signs of disturbed motor control. Impaired motor control is predominantly associated with damaged voxels within the SMC and the anterior and medial cingulate cortex, while lesions within the pre-SMA are specifically related to AHS. No BP was detected over the damaged hemisphere. ACA strokes involving the premotor cortices, particularly the pre-SMA, are associated with AHS-specific signs. In the acute phase, motor behavior is characterized by the inability to carry out self-initiated movements. Motor control deficits may persist to a variable degree beyond the acute phase. Alterations of the BP point to an underlying SMC dysfunction in AHS.
Highlights
Voluntary and involuntary movements are generated and controlled by a complex bihemispheric neuronal network involving the primary motor (MI) and supplementary motor complex [SMC; consisting of the supplementary motor area (SMA) proper and pre-SMA], cingulate cortex, and dorsolateral prefrontal cortex as well as a number of subcortical brain structures such as the basal ganglia and the cerebellum
According to the TOAST criteria [32], macroangiopathy was identified as a stroke etiology in 3/10 patients, cardioembolic events in 6/10, and arterial emboli secondary to aneurysm coiling in the anterior cerebral artery (ACA) in 1/10
In our case series, which is one of the largest imaging-based studies in alien hand syndrome (AHS) patients, we found a wide spectrum of clinical signs related to disturbed motor control ranging from very mild presentations with only transient impairment to very severely affected cases
Summary
Voluntary and involuntary movements are generated and controlled by a complex bihemispheric neuronal network involving the primary motor (MI) and supplementary motor complex [SMC; consisting of the supplementary motor area (SMA) proper and pre-SMA], cingulate cortex, and dorsolateral prefrontal cortex as well as a number of subcortical brain structures such as the basal ganglia and the cerebellum. Motor areas supplied by the anterior cerebral artery (ACA) involve the SMC, the anterior and middle cingulate cortex, and the rostral section of the corpus callosum. This part of the motor network is involved in the generation of self-initiated (i.e., volitional), complex movement sequences, inhibition of purposeless movements triggered by external stimuli such as the grasp reflex, error control during motor performance, and motor learning [1, 2]. By applying direct electrical stimulation to the SMC, a conscious intention of moving can be provoked underlining its role in generating volitional movements [6] Both the supplementary motor complex (SMC), consisting of the supplementary motor area (SMA) proper, the pre-SMA, and the supplementary eye field, and the rostral cingulate cortex are supplied by the anterior cerebral artery (ACA) and are involved in higher motor control. ACA strokes may lead to impaired motor control in the absence of limb weakness and evoke an alien hand syndrome (AHS) in its extreme form
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