Other medical conditions. Delirium and NCDs due to side effects of dopamine-blocking drugs and other medical conditions (e.g., sedation or impaired cognition, severe hypothy- roidism, B12 deficiency) must also be ruled out.
Parkinson’s disease may coexist with Alzheimer’s disease and cerebrovascular disease, espe- cially in older individuals. The compounding of multiple pathological features may diminish the functional abilities of individuals with Parkinson’s disease. Motor symptoms and frequent co—occurrence of depression or apathy can make functional impairment worse.
Due to Huntington’s Disease
A. The criteria are met for major or mild neurocognitive disorder.
B. There is insidious onset and gradual progression.
C. There is clinically established Huntington‘s disease, or risk for Huntington’s disease based on family history or genetic testing.
Major or Mild Neurocognitive Disorder Due to Huntington’s Disease 639
D. The neurocognitive disorder is not attributable to another medical condition and is not better explained by another mental disorder.
Coding note: For major neurocognitive disorder due to Huntington’s disease, with behav- ioral disturbance, code first 333.4 (610) Huntington’s disease, followed by 294.11 (F02.81) major neurocognitive disorder due to Huntington’s disease, with behavioral dis- turbance. For major neurocognitive disorder due to Huntington’s disease, without behav- ioral disturbance, code first 333.4 (610) Huntington's disease, followed by 294.10 (F02.80) major neurocognitive disorder due to Huntington’s disease, without behavioral disturbance.
For mild neurocognitive disorder due to Huntington’s disease, code 331.83 (631.84).
(Note: Do not use the additional code for Huntington's disease. Behavioral disturbance cannot be coded but should still be indicated in writing.)
Progressive cognitive impairment is a core feature of Huntington’s disease, with early changes in executive function (i.e., processing speed, organization, and planning) rather than leam- ing and memory. Cognitive and associated behavioral changes often precede the emergence of the typical motor abnormalities of bradykinesia (i.e., slowing of voluntary movement) and chorea (i.e., involuntary jerking movements). A diagnosis of definite Huntington’s dis- ease is given in the presence of unequivocal, extrapyramidal motor abnormalities in an in- dividual with either a family history of Huntington’s disease or genetic testing showing a
CAG trinucleotide repeat expansion in the HTT gene, located on chromosome 4.
Depression, irritability, anxiety, obsessive-compulsive symptoms, and apathy are fre- quently, and psychosis more rarely, associated with Huntington’s disease and often pre- cede the onset of motor symptoms.
Neurocognitive deficits are an eventual outcome of Huntington’s disease; the worldwide prevalence is estimated to be 2.7 per 100,000. The prevalence of Huntington’s disease in
North America, Europe, and Australia is 5.7 per 100,000, with a much lower prevalence of 0.40 per 100,000 in Asia.
The average age at diagnosis of Huntington’s disease is approximately 40 years, although this varies widely. Age at onset is inversely correlated with CAG expansion length. Juve- nile Huntington’s disease (onset before age 20) may present more commonly with brady- kinesia, dystonia, and rigidity than with the choreic movements characteristic of the adult- onset disorder. The disease is gradually progressive, with median survival approximately 15 years after motor symptom diagnosis.