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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. |
