History
The first symptoms typically are choreic movements or psychiatric disorders, whereas global cognitive decline generally becomes obvious later and eventually expresses itself as a triad of disordered movement, cognitive decline, and psychiatric disturbance. Clinically, the cognitive deterioration of HD is generally thought to correlate with the number of years affected rather than the age of onset. In a study conducted by Jason et al, cognitive manifestations were examined in relation to age, clinical onset, progression, and genetic analysis. [5] Evidence showed an inverse correlation between the age of onset of cognitive impairment and the number of trinucleotide repeats in the HD gene. Additionally, this study showed that, although a statistically significant correlation exists between the number of repeats and the progressive dementia, the relationship is tenuous.
Psychiatric symptoms are prominent in patients with HD, as follows:
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Symptoms range from personality alterations to mood disorders, aggressiveness, hypersexuality or impotence, alcoholism, and psychosis, including schizophrenia.
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Psychiatric disorders may occur in 35–73% of patients with HD, and behavioral changes may represent the initial manifestation of the disease in one third to one half of the cases.
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Depression is the most common psychiatric condition.
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Mania occurs in 2–12% of patients, whereas suicide occurs in nearly 6% of patients.
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Eccentricity, inappropriateness, loss of social amenities, excess irritability, and sexual hyperactivity can mark the early stages.
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Occasionally, a schizophreniform illness precedes the motor abnormality by several years.
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Depression, apathy, social withdrawal, and intermittent disinhibition are common.
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The prevalence of apathy (Apathy Scale score 14 points) in patients with Huntington Disease is independently associated with male sex, worse global functioning, and the higher use of neuroleptics and benzodiazepines. [6]
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Suicide occurs frequently, partially because the progressing dementia often fails to blunt insight.
When HD starts as subtle fidgeting, it may be unrecognized by the patient and family. Patients have a history of progressive generalized choreiform activity accompanied by behavioral or personality changes, especially in those with a family history. Sporadic cases are also possible.
Causes
HD is a genetic autosomal dominant disorder. Persons who have 36 or more CAG repeats in the HD gene have inherited the disease mutation and eventually develop symptoms if they live to an advanced age. Each of their children has a 50% risk of inheriting the abnormal gene. Also, rare sporadic cases without any family history occur.
Physical Examination
See the list below:
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Early motor symptoms often include dystonic posturing and rigidity, but these changes give way to prominent choreiform activity in most affected adults.
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Frequent, irregular, and sudden jerks and movements of any of the limbs or trunk occur.
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Grimacing, grunting, and poor articulation of speech may be prominent.
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Mental status exam
The patient appears older than stated age.
Patient is well oriented in all spheres.
Patient appears alert.
Affect is appropriate.
Mood is euthymic.
Presents self in a disheveled and sloppy fashion.
Eye contact can be described as limited.
Speech is illogical, incoherent, garbled, and not goal-directed.
An increased risk for suicidal and homicidal thinking occurs due to the poor prognosis and erratic thinking, which can be accompanied by paranoia.
Recent memory appears moderately to severely impaired. Remote memory is not impaired.
Psychomotor activity can be characterized by choreic movements and hyperactivity.
A negligible to severe degree of conceptual disorganization is evident.
Thought content is characterized by delusions, hallucinations, and violent ideation at times.
Regarding perceptual functioning, the patient has hallucinations and none are evident.
Attitude can be described as cooperative but disinterested.
The patient verbalizes no awareness of problems and does not see consequences. Judgment is poor.
Attention/concentration is characterized by an inability to attend and maintain focus.
The patient is not reflective and unable to resist urges.
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The gait is disjointed and poorly coordinated. Patients with HD, like healthy subjects, depend more on proprioceptive cues than on visual cues to maintain balance; however, patients with HD develop more sway compared with healthy subjects when proprioceptive cues and vision are altered.
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Given the presence of choreiform movement and subcortical neuropathology, performance on manual dexterity tasks is impaired.
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Cognitive symptoms include the following:
Memory frequently is not impaired until late in the disease, but attention, judgment, and executive functions may be seriously deficient at an early stage.
Early signs of dementia often include forgetfulness, disorganization, and affective disorders.
Free recall may be severely impaired.
Memory deficits involve both recent and remote function. Studies show that patients with HD can accurately recognize recently presented verbal material only when cues are used in memory retrieval. Other studies show that the patients sometimes recall words the next day that they had not recalled during testing sessions, further supporting a delayed-retrieval hypothesis.
Patients have significant problems with frontal executive functions, such as problems with maintenance, cognitive flexibility, abstraction, judgment, reasoning, sequencing, organizing, planning, and adapting.
Skilled motor-procedural learning deficits are reported. Working memory may be affected in patients with HD because of frontal lobe dysfunction associated with the bidirectional connections with the caudate.
Insight, orientation, factual information, and overall intelligence quotient scores are preserved relatively well into the disease process.
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Verbal skills are discussed as follows:
Verbal skills are the least impaired in patients with HD.
Reduced fluency in the face of preserved confrontation naming occurs.
Letter and category fluency are also impaired.
Sensory motor deficits occur, such as poor olfactory perception, slow sequential or graphomotor movements, and impaired prism adaptation.
Solomon et al found that verbal episodic memory function is affected in patients with HD CAG expansion, in a manner that is consistent with the profile of subcortical dementias, prior to manifestation of HD. [7] The authors concluded that impairments in verbal learning and memory are detectable prior to clinical diagnosis of HD. Identifying the presentation of such features early provides clinicians with the opportunity to monitor the course of progression. The study was part of the ongoing Predict-HD project through which researchers are seeking to identify markers that will enable tracking of the disease from its earliest stages.
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Spatial disorientation, specifically the inability to identify position relative to a fixed point, is another characteristic impairment in patients with HD. In a landmark study conducted by Podegil et al, patients with HD were asked to remember the position of a fixed target and then were asked to identify the point after being blindfolded. The patients were able to identify the markings in this setting; yet, when a variation of position was incorporated (ie, sidestepping after being blindfolded), patients showed significant impairment in target localization.
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Patients with HD have difficulty in sustaining their performance in a variety of everyday tasks that require both cognitive and motor function. Performance on the Stroop test and the Trail-Making Test are highly sensitive to these deficits, which encompass activities associated with mental arithmetic, digit or symbol matching, and reaction time.
