Slowly progressive limb-kinetic apraxia with a decrease in unilateral cerebral blood flow

A progressive breakdown of the body in space

A 74 year-old woman (MD), free of previous neurological history, presented with difficulty in handling cutlery, clothes, writing with what was initially described as an atypical apraxia in acts related to space. Initial neurological evaluation revealed mixed, asymmetric pyramidal, and extrapyramidal semiology. Νeuropsychological testing revealed dressing and constructional deficits, ideomotor apraxia and signs of executive dysfunction in absence of memory, language, and visual perception pathology. The final diagnosis was that of a corticobasal degeneration, where the rare occurrence of a progressively emerging syndrome of self-management loss within peripersonal space is observed.

Is progressive upper-body apraxia a corticobasal syndrome?

Corticobasal degeneration (CBD) is characterized by various clinical manifestations including corticobasal syndrome, progressive supranuclear palsy-like syndrome and frontotemporal dementia. Focal cortical atrophy syndrome as the initial manifestation rarely occurs in CBD. Here, we present a 62-year-old man and a 70-year-old man who were admitted due to clumsiness in the arms. On initial neurological examination, they showed asymmetric limb apraxia without parkinsonism or global cognitive dysfunction. Brain MRI showed focal atrophy in the frontal and prefrontal cortices, and brain positron emission tomography scan revealed decreased metabolism in these same brain locations. Although these patients developed parkinsonism and dystonia within several years, the neurological signs were limited to the arms for a long period. "Progressive upper-body apraxia" may be a rare clinical manifestation of CBD which shows a benign clinical outcome. The patients described may enhance our understanding of the clinical heterogeneity of this disease.

Apraxia in movement disorders

The definition of apraxia specifies that the disturbance of performed skilled movements cannot be explained by the more elemental motor disorders typical of patients with movement disorders. Generally this does not present a significant diagnostic problem when dealing with 'higher-level' praxic disturbances (e.g. ideational apraxia), but it can be a major confound in establishing the presence of limb-kinetic apraxia. Most motor disturbances characteristic of extrapyramidal disorders, particularly bradykinesia and dystonia, will compromise the ability to establish the presence of loss of dexterity and deftness that constitutes this subtype. The term 'apraxia' has also been applied to other motor disturbances, such as 'gait apraxia' and 'apraxia of eyelid opening', that perhaps are misnomers, demonstrating the lack of a coherent nomenclature in this field. Apraxia is a hallmark of corticobasal degeneration (CBD) and historically this has received the most attention among the movement disorders. Corticobasal degeneration is characterized by various forms of apraxia affecting limb function, particularly ideomotor apraxia and limb-kinetic apraxia, although buccofacial and oculomotor apraxia can be present as well. The syndrome of parkinsonism and prominent apraxia, designated the 'corticobasal syndrome' (CBS), may be caused by a variety of other central nervous system pathologies including progressive supranuclear palsy (PSP), Alzheimer's disease, dementia with Lewy bodies and frontotemporal dementias. Distinct from the CBS, PSP and Parkinson's disease can demonstrate varying degrees of apraxia on selected tests, especially in those patients with more severe cognitive dysfunction. Diseases that cause the combination of apraxia and a primary movement disorder most often involve a variety of cerebral cortical sites as well as basal ganglia structures. Clinical-pathological correlates and functional imaging studies are compromised by both this diffuse involvement and the confusion experienced in the clinical evaluation of apraxia in the face of the additional elemental movement disorders. Finally, although apraxia results in clear disability in patients with the CBS, it is not clear how milder ideomotor apraxia found on specific testing contributes to patients' overall day-to-day motor disability.

Corticobasal degeneration as a cognitive disorder

The presence of cognitive impairment in corticobasal degeneration (CBD) is now widely recognised. Our review of the literature reveals that, although the pattern and severity of neuropsychological impairments can be highly variable across patients, several general trends can be identified. The most characteristic impairments are limb apraxia (usually ideomotor), constructional and visuospatial difficulties, acalculia, frontal dysfunction, and nonfluent aphasia. The limb apraxia is associated with deficits in drawing, copying, and handwriting, but there is emerging evidence that the problems with handwriting are not due exclusively to the apraxia. The findings with respect to episodic memory are more variable, but when there is impairment in this area, it tends to be milder than that seen in Alzheimer's disease. Semantic memory functioning appears relatively preserved but has been poorly studied. Problems with speech are common, and may be due to dysarthria or buccofacial apraxia. Aphasia, although initially considered rare, is in fact a common accompaniment of CBD, may be the presenting feature, and is typically nonfluent in type. More systematic investigation of the clinical and neuropathological overlap between progressive nonfluent aphasia (generally considered to be a form of frontotemporal dementia) and CBD is needed.

Limb-kinetic apraxia in corticobasal degeneration: clinical and kinematic features

Current concepts regarding the organisation of the motor system indicate the existence of a frontoparietal circuit involved in prehension and manipulation, whose damage may result in a motor behavioural disorder strongly resembling the one originally described as limb-kinetic apraxia. To determine the specific clinical and kinematic features of this distinctive praxic disorder, 5 patients with corticobasal degeneration (apraxic group), 5 with Parkinson's disease (nonapraxic group), and 10 control subjects were studied by a comprehensive apraxic battery, three-dimensional motion analysis of manipulative movements and motor evoked potentials. A mathematical model [quality of movement coefficient (QMC)] was applied to quantify differential kinematic characteristics between elementary motor deficits and the praxic disorder. Transcranial magnetic stimulation was used to evaluate corticomotoneural projections and cortical inhibition. All five patients in the apraxic group exhibited a unilateral praxic deficit characterised by derangement of fractionated and segmental finger movements. QMC was significantly greater in apraxic than in nonapraxic patients (P < 0.02), revealing a chaotic movement with marked interfinger uncoordination. Conventional transcranial magnetic stimulation parameters were within normal limits in both groups of patients; however, the silent period was significantly shorter in the apraxic limb when compared with control subjects (P < 0.001). Limb-kinetic apraxia is a distinctive disorder affecting the performance of finger and hand postures and movements over and above a corticospinal or basal ganglion deficit. Disruption of the frontoparietal circuit devoted to grasping and manipulation, together with defective cortical inhibition, which would also interfere with the selection and control of hand muscle activity, are the most likely underlying physiopathological mechanisms of limb-kinetic apraxia in patients with corticobasal degeneration.

Truncal and limb apraxia in corticobasal degeneration

We report a patient with probable corticobasal degeneration with prominent truncal apraxia, and review the literature.

Limb apraxias: higher-order disorders of sensorimotor integration

Limb apraxia comprises a wide spectrum of higher-order motor disorders that result from acquired brain disease affecting the performance of skilled, learned movements. At present, limb apraxia is primarily classified by the nature of the errors made by the patient and the pathways through which these errors are elicited, based on a two-system model for the organization of action: a conceptual system and a production system. Dysfunction of the former would cause ideational (or conceptual) apraxia, whereas impairment of the latter would induce ideomotor and limb-kinetic apraxia. Currently, it is possible to approach several types of limb apraxia within the framework of our knowledge of the modular organization of the brain. Multiple parallel parietofrontal circuits, devoted to specific sensorimotor transformations, have been described in monkeys: visual and somatosensory transformations for reaching; transformation of information about the location of body parts necessary for the control of movements; somatosensory transformation for posture; visual transformation for grasping; and internal representation of actions. Evidence from anatomical and functional brain imaging studies suggests that the organization of the cortical motor system in humans is based on the same principles. Imitation of postures and movements also seems to be subserved by dedicated neural systems, according to the content of the gesture (meaningful versus meaningless) to be imitated. Damage to these systems would produce different types of ideomotor and limb-kinetic praxic deficits depending on the context in which the movement is performed and the cognitive demands of the action. On the other hand, ideational (or conceptual) apraxia would reflect an inability to select and use objects due to the disruption of normal integration between systems subserving the functional knowledge of actions and those involved in object knowledge.

Cerebral blood flow correlates of higher brain dysfunctions in corticobasal degeneration

To investigate clinicoanatomic correlations of higher brain dysfunctions in corticobasal degeneration, regional cerebral blood flow (rCBF) was semiquantitatively measured with single-photon emission computed tomography in 9 patients with corticobasal degeneration and 12 age-matched control subjects. The patients showed significant reductions of relative tracer uptake in widespread cortical areas, as well as the basal ganglia and thalamus. Interhemispheric difference of hypoperfusion was significant in the sensorimotor and posterior parietal cortices. Asymmetric limb apraxia and cortical sensory disturbance corresponded to either sensorimotor cortical or posterior parietal cortical hypoperfusion or both. Compared with the patients without dementia, those with dementia showed significant reductions of relative rCBF in the inferior prefrontal region in the more affected hemisphere. The unique correlation of cortical signs with regional hypoperfusion may be useful in distinguishing between corticobasal degeneration and other neurodegenerative diseases.

Cerebral blood flow in corticobasal degeneration and progressive supranuclear palsy

To compare brain perfusion between corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP), we investigated regional cerebral blood flow (rCBF) semiquantitatively with single-photon emission computed tomography and [123I]iodoamphetamine in six patients with CBD and five with PSP. Compared with 12 age-matched control subjects, the average of the left and right rCBF values for the CBD patients was significantly reduced in the inferior prefrontal, anterior cingulate, medial premotor, sensorimotor, posterior parietal, and superior temporal cortices as well as in the basal ganglia and thalamus, whereas only the medial premotor cortex was significantly hypoperfused in the PSP patients. Compared with the PSP patients, the CBD patients showed significantly decreased rCBF in the inferior prefrontal, sensorimotor, and posterior parietal cortices, but not in the subcortical regions. Compared with the controls, interhemispheric differences of rCBF were significant in the inferior prefrontal, sensorimotor, and posterior parietal cortices of the CBD patients but in only the medial prefrontal cortex of the PSP patients. These results indicate that rCBF reductions are more extensive and asymmetric in CBD than in PSP, although the two diseases share medial frontal involvement.

Neuropsychological and neuroimaging correlates in corticobasal degeneration

The aim of this study was to correlate neuropsychological and neuroimaging findings in corticobasal degeneration (CBD). Three patients with clinical criteria for CBD were examined by means of neuropsychological tests, brain magnetic resonance imaging (MRI), and flow and metabolism neuroimaging techniques. Neuropsychological assessment revealed impairment in executive functions, manual dexterity and motor programming with significant asymmetry between upper limbs. Ideomotor and oral apraxia were also detected, and memory deficits were observed in one patient. MRI revealed cortical dilation of the frontal and peri-rolandic regions, symmetrical in one case and asymmetrical in the other two cases. An increased T2 signal intensity in the posterolateral putamen and substantia nigra ipsilateral to the cortical atrophy was observed in one patient. Asymmetries of both frontal and parietal cortices and basal ganglia were detected in all three patients by 18-fluorodeoxyglucose positron emission tomography; temporal region hypometabolism was associated in one patient. These cortical and subcortical asymmetries were observed in two patients by single photon emission tomography with the tracer technetium Tc 99m hexamethyl propylenamine oxime; cortical asymmetry was observed in only one patient. The results showed that functional neuroimaging findings correlated well with neuropsychological aspects in CBD. Neuroimaging and neuropsychological correlations may contribute toward understanding anatomical and functional abnormalities associated with this neurodegenerative disorder.

Asymmetric changes in somatosensory evoked potentials correlate with limb apraxia in corticobasal degeneration

To clarify the underlying mechanism of limb apraxia in corticobasal degeneration (CBD), we investigated somatosensory evoked potentials in 5 patients with CBD, as compared with 12 age-matched control subjects. All patients presented with asymmetric limb apraxia, particularly of limb-kinetic type. N20 latencies were significantly prolonged following median nerve stimulation on the more apraxic side, but not on the less apraxic side. These results suggest that limb apraxia in CBD may, at least in part, be due to a disorder of somatosensory information processing involving the parietal cortex.

Electrophysiological comparison between corticobasal degeneration and progressive supranuclear palsy

Multimodal evoked potentials were recorded in four patients with corticobasal degeneration (CBD), four patients with progressive supranuclear palsy (PSP) and 15 normal control subjects. CBD and PSP patients showed significant prolongation of the N200 and P300 latencies of auditory event-related potentials compared with controls. Patients with CBD showed significant prolongation of interpeak latencies between N13 and N20 of short-latency somatosensory evoked potentials compared with the controls and patients with PSP. The present results show that the two diseases have different electrophysiologic features.

Pure progressive clumsiness due to parietal atrophy in a young adult

Progressive clumsiness developed in the right hand of a 33-year-old man, became bilateral and evolved very slowly for ten years. Another neurological deficit was restricted to a slight impairment of superficial sensations. Magnetic resonance imaging verified an atrophy of bilateral parietal lobes. The cerebral blood flow was markedly decreased in the atrophic area. Pure clumsiness of a very slowly progressive course due to parietal atrophy has never been reported in such a young adult. This clinical picture may suggest another variety of degenerative process.

Focal cortical hypoperfusion in corticobasal degeneration demonstrated by three-dimensional surface display with 123I-IMP: a possible cause of apraxia

To clarify cortical lesions responsible for apraxia in cortico-basal degeneration (CBD), we reconstructed three-dimensional surface images from single-photon emission computed tomography (SPECT) data with N-isopropyl-p[I-123]-iodoamphetamine in two patients with CBD. Both had limb-kinetic apraxia (LKA) and one also had constructional apraxia (CA). Both showed asymmetrical cortical hypoperfusion in the perirolandic area. The patient with CA had unilateral hypoperfusion in the posterior parietal area. Thus, cortical hypoperfusion in the perirolandic area corresponded to LKA, and that in the posterior parietal area to CA.

Slowly progressive apraxia in Alzheimer's disease

Slowly progressive apraxia due to Alzheimer's disease was encountered in a 66 year old, right handed man whose initial impairments included coordinated movements of the left hand and some features of the alien hand syndrome. Over four years, the patient developed progressively worsening deficits of memory and language. A biopsy of his right temporal lobe showed numerous plaques and neurofibrillary tangles. Pronounced right parietal lobe hypoperfusion on serial SPECT suggests involvement of this region in contralateral praxis.

The nature of apraxia in corticobasal degeneration

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