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Awareness of Involuntary Movements
in Huntington Disease
Julie S. Snowden, PhD.
Objective:
To determine why patients with Huntington's disease are apparently unaware of their involuntary movements.
 
Design: 
Correlative study using a subjective report questionnaire of physical symptoms and Objective measures of neurologic and cognitive dysfunction.
 
Patients:
Forty patients with Huntington disease attending a regional Huntington disease clinic.
 
Results:
Patients were poor at reporting experiential symptoms of involuntary movements. There was no relationship between self-report of these symptoms and objective indices of motor dysfunction or severity of cognitive impairment. Patients could, however, report secondary consequences of their movement disorder, which correlated highly with nonchoreic indices of motor dysfunction.
 
Conclusions:
Patients with Huntington disease have impaired subjective experience of chorea. Denial of symptoms is likely to have a physiological basis and is not a secondary consequence of patients' cognitive impairment or a psychological defense against a debilitating disease.
 
DISCUSSION

Patients with  Huntington disease (HD) rarely complain of their involuntary movements. Although the phenomenon is well recognized clinically, its basis has not been systematically investigated.

A common implicit assumption is that lack of awareness of movement disorder is one manifestation of a general reduction in insight as a result of patients' accompanying dementia.

Such an interpretation is feasible given the nature of cognitive changes in patients with HD. It is well established that patients exhibit impairments in regulatory, control functions, akin to those associated with frontal lobe lesions and that such lesions are commonly associated with impaired insight.

An alternative common assumption is that patients' failure to acknowledge motor symptoms results from a denial of illness and represents a psychological defense against the onslaught of a distressing and debilitating disease.

A third, more prosaic, explanation is also possible. Patients may fail to report involun-tary movements for the simple reason that they do not experience moving abnormally. Patients may not receive internal feedback about the movement of their limbs that would lead to the subjective experience of involun-tary movement.

The purpose of this study was to attempt to distinguish between these cognitive, psycho-dynamic, and physiological explanations.

Conversely, cognitive and psycho-dynamic explanations predict no such disparity.

The physiological hypothesis predicts that patients with HD should be better at reporting the consequences of their abnormal move-ments, such as dropping objects, spilling drinks, and bumping into furniture, rather than the actual experience of the movements themselves. Patients, while not experiencing abnormal movements directly, would nevertheless be aware of their secondary effects. Conversely, cognitive and psycho-dynamic explanations predict no such disparity.

A lack of insight due to frontal cognitive failure would be expected to extend to the consequences as well as the direct experience of involuntary movements.

Similarly, a psychological defense mechanism of denial should lead to a systematic failure to report both the experience of movements and their practical consequences.

Our study used a subjective report questionnaire, with questions pertaining to the direct experience of involuntary movements or to the consequences of the movement disorder.

Subjective reports were examined in relation to objective measures of neurologic and cognitive dysfunction.

Commment

Most patients with HD in the study reported some physical symptoms on specific questioning. However, patients were more likely to report symptoms pertaining to the consequences of movement disorder, such as dropping objects, than the direct experience of involuntary movements, such as feelings of twitching in the fingers.

Statistical analyses, using a measure of association, revealed no relationship between direct experience measures and objective indices of movement disorder, in particular of chorea, which the direct experience questions were designed to tap. Involuntary movements that were detected on neurologic examination were poorly reported by patients themselves.

This finding cannot be attributed to a general loss of insight into the movement disorder, since reports of the conse-quences of abnormal movements were significantly correlated with objective measures of movement disorder: the more subjective the symptoms, the poorer the QNE scores.

These findings suggest that patients fail to experience involuntary movements, yet are aware of the consequences of their movement disorder.

Comment continued

These findings suggest that patients fail to experience involuntary movements, yet are aware of the consequences of their movement disorder.

  • What do the consequence measures actually measure?
  • Do they represent the secondary consequences of the involuntary movements per se, or alter-natively, do they reflect impair-ment in the voluntary aspects of the movement disorder?

The finding that consequence-type symp-toms were strongly related to nonchoreic aspects of the movement disorder but were unrelated to measures of chorea is relevant in this regard. It suggests that the consequence-type symptoms represent the effects of nonchoreic aspects of the move-ment disorder, such as bradykinesia, and not of chorea.

Such a view is supported, moreover, by the cognitive test data. Significant relationships with cognitive test performance occurred only for consequence-type symptoms, and the strongest relationships were with tests that have high demands on motor speed.

Patients who performed more slowly on these tasks reported more consequence-type symptoms. The finding of a significant correlation between conse-quence-type symptoms and functional capacity would imply that it is nonchoreic aspects of movement disorder and not chorea that leads to functional disability. Indeed, chorea has been shown to be unrelated to functional decline.

Since subjective reports accurately reflect components of the movement disorder such as motor slowing, they suggest that patients may experience those aspects of their disorder. It is specifically the choreiform movements of which patients with HD are unaware.

These findings rule out a psychodynamic explanation of patients' unawareness of chorea: it is not that patients are denying physical symptoms. Indeed, some symptoms would appear to be reported accurately because of their association with objec-tive measures of movement disorder.

The cognitive hypothesis also can be excluded. There was no significant relationship between failure to report physical symptoms and severity of cognitive impairment, in particular, frontal lobe dysfunction.

Indeed, the few significant relationships were in the reverse direction: having fewer symptoms was associated with superior cognitive test performance compatible with milder illness. That the strongest association was with timed tasks (recitation and reversal of the months of the year and word reading) suggests that the physical symptoms that patients with HD accurately report relate to their physical slowing (bradykinesia).

Our findings are consistent with the physiological hypothesis: patients with HD fail to complain of their involuntary movements because they do not have a subjective experience of chorea. They appear to be aware only of the reper-cussions of their movement disorder, or more precisely those aspects of their movement disorder, such as physical slowing, that are distinct from chorea.

This apparent dissociation in awareness for different components of the move-ment disorder is not unique to HD. A parallel phenomenon is commonly observed in patients with Parkinson disease.

Patients who are distressed with their bradykinesia may nonetheless appear oblivious to their drug-induced dyskin-esias. The physiological hypothesis requires critical scrutiny by future studies.

The precise mechanisms that might underlie the experience or lack of experience of movement remain to be discerned. Nevertheless, the physio-logical hypothesis is important in highlighting a viable alternative to the traditional interpretations of why patients with HD fail to report chorea.

These findings have implications for the treatment and management of HD.

These findings have implications for the treatment and management of HD. In the past the use of dopamine-depleting drugs, such as tetrabenazine, for the treatment of chorea was widespread.     In recent years their use in HD has become more restricted on the grounds that such pharmacological agents may exacerbate motor disability and increase patients' predisposition to functionally disabling symptoms, such as depression.

Our finding that patients with HD are unaware of their choreiform move- ments....It would seem inappropriate to treat an aspect of motor disorder of which the patient is unaware with agents that may worsen those aspects of motor dysfunction for which the patient does have awareness and that are associated with greatest functional disability.

Our finding that patients with HD are unaware of their choreiform move- ments reinforces the validity of that conservative position. It would seem inappropriate to treat an aspect of motor disorder of which the patient is unaware with agents that may worsen those aspects of motor dysfunction for which the patient does have awareness and that are associated with greatest functional disability.

Our findings also have relevance to the understanding of HD.  Patients who fail to report symptoms should not be dismissed as demented or in denial. Their failure to report symptoms reflects their subjective experience.

Clinicians who inform patients newly diagnosed as having HD that they have the disease should bear in mind that the chorea that is so immediately apparent to the external observer may not be within the subjective experience of the patients themselves.

Reprints: Julie S. Snowden, PhD, Department of Neurology, Manchester Royal infirmary, Manchester MI139WL,England.