Neurocognitive Disorder Due to Huntington’s Disease

What Is Huntington’s Disease?

Huntington’s disease (HD) is an inherited disorder that causes brain cells, called neurons, to die in various areas of the brain, including those that help to control voluntary (intentional) movement. Symptoms of the disease, which gets progressively worse, include uncontrolled movements (called chorea); abnormal body postures; and changes in behavior, emotion, judgment, and cognition. People with Huntington’s disease (HD) also develop impaired coordination, slurred speech, and difficulty feeding and swallowing. Huntington’s disease (HD) typically begins between ages 30 and 50. An earlier onset form called juvenile HD occurs under age 20. HD’s symptoms differ somewhat from adult-onset HD and include rigidity, slowness, difficulty at school, rapid involuntary muscle jerks called myoclonus, and seizures. More than 30,000 Americans have HD.

Huntington’s disease is caused by a mutation in the gene for a protein called huntingtin. The defect causes the cytosine, adenine, and guanine (CAG) building blocks of DNA to repeat many more times than is normal. Each child of a parent with HD has a 50-50 chance of inheriting the HD gene. A child who does not inherit the HD gene will not develop the disease and generally cannot pass it to subsequent generations. A person who inherits the HD gene will eventually develop the disease. HD is generally diagnosed based on a genetic test, medical history, brain imaging, and neurological and laboratory tests.

The essential feature of neurocognitive disorder due to Huntington’s disease (HD) is the presence of dementia that is judged to be the direct pathophysiological consequence of Huntington’s disease.

Diagnostic Criteria

• The criteria are met for major or mild neurocognitive disorder.
• There is insidious onset and gradual progression.
• There is a clinically established Huntington’s disease, or risk for HD based on family history or genetic testing.
• The neurocognitive disorder is not attributable to another medical condition and is not better explained by another mental disorder.

Differential Diagnosis

Early symptoms of Huntington’s disease may include instability of mood, irritability, or compulsive behaviors that may suggest another mental disorder. However, genetic testing or the development of motor symptoms will distinguish the presence of Huntington’s disease.

The early symptoms of Huntington’s disease, particularly symptoms of executive dysfunction and impaired psychomotor speed, may resemble other neurocognitive disorders (NCDs), such as major or mild vascular NCD.

Prognosis

Treatment

Substance Abuse

Research over the last two decades has demonstrated that abuse of psychostimulants results in several cognitive deficits such as impulsivity (i.e., inability to inhibit disadvantageous rapid behavioral responses), risky and/or poor decision-making, impaired cognitive flexibility (i.e., impaired ability to alter behavioral responses based on changing environmental contingencies), deficits in learning and memory, and/or hyperattentiveness. Interestingly, individuals with pre-existing deficits in cognition and/or suffering from psychiatric disease states that are associated with impaired cognitive function (e.g., schizophrenia and depression) are more vulnerable to abusing illicit and licit stimulants. Importantly, recovering addicts with significant cognitive deficits are more vulnerable to relapse. Cognitive deficits in recovering drug addicts irrespective of whether they were pre-existing or drug-induced need to be adequately treated to promote abstinence among drug addicts.^[1]

Alcohol-related dementia (ARD) is a broad term currently preferred among medical professionals. Many experts use the terms alcohol (or alcoholic) dementia to describe a specific form of ARD, characterized by impaired executive function (planning, thinking, and judgment). Another form of ARD is known as wet brain (Wernick-Korsakoff syndrome), which is characterized by short-term memory loss and a thiamine (vitamin B1) deficiency. ARD patients often have symptoms of both types of ARD that include impaired ability to plan, apathy, and memory loss. ARD may occur with other forms of dementia (mixed dementia). The diagnosis of ARD is widely recognized but rarely applied, due to a lack of specific diagnostic criteria.

Alcohol-related dementia presents as a global deterioration in intellectual function not specific to memory but it may also occur with other forms of dementia therefore resulting in a wide range of symptoms. Certain individuals with alcohol-related dementia present with damage to the frontal lobes of their brain causing disinhibition, loss of planning and executive functions, and a disregard for the consequences of their behavior. Other types of alcohol-related dementia such as Korsakoff’s syndrome cause the destruction of certain areas of the brain, where changes in memory, primarily a loss of short-term memory, are the main symptom. Most presentations of alcohol dementia are somewhere along the spectrum between global dementia and Korsakoff’s psychosis and may include symptoms of both.

Individuals affected by alcohol-related dementia may develop memory problems, language impairment, and an inability to perform complex motor tasks such as getting dressed. People with heavy alcohol abuse may develop cerebellar ataxia, which consists of damages the nerves in arms and legs, i.e., peripheral neuropathy as well as the cerebellum. These patients frequently have problems with sensation in their extremities and may demonstrate unsteadiness on their feet.

Alcohol-related dementia can produce a variety of psychiatric problems including psychosis (disconnection from reality), depression, anxiety, and personality changes. Patients with alcoholic dementia often develop apathy, related to frontal lobe damage, which may mimic depression. People with alcoholism are more likely to become depressed than people without alcoholism, and it may be difficult to differentiate between depression and alcohol dementia. Epidemiological studies show an association between long-term alcohol intoxication and dementia. Alcohol can damage the brain directly as a neurotoxin, or it can damage it indirectly by causing malnutrition, primarily a loss of thiamine (vitamin B1). Approximately 10% of all dementia cases are related to alcohol consumption, making it the second leading cause of dementia.^[2]

Traumatic Brain Injury (TBI)

Traumatic brain injury (TBI) occurs when an individual experiences a significant trauma or injury to the head. Neurocognitive disorder due to traumatic brain injury (TBI) is diagnosed when persistent cognitive impairment is observed immediately following the head injury, along with one or more of the following symptoms: loss of consciousness, posttraumatic amnesia, disorientation, and confusion or neurological impairment (APA, 2013).

Each year, traumatic brain injury (TBI) is responsible for more than 80,000 emergency department visits for those above age 65, approximately three-quarters of which result in hospitalization. The leading causes of TBI include fallsand motor vehicle accidents.^[3] TBI is present in 85% of traumatically injured children, either alone or with other injuries. The greatest number of TBIs occur in people aged 15–24. The age groups most at risk for TBI are children ages five to nine and adults over age 80, and the highest rates of death and hospitalization due to TBI are in people over age 65. The incidence of fall-related TBI in first-world countries is increasing as the population ages; thus the median age of people with head injuries has increased.

Regardless of age, TBI rates are higher in males. Men suffer twice as many TBIs as women do and have a fourfold risk of fatal head injury, and males account for two-thirds of childhood and adolescent head trauma. However, when matched for severity of injury, women appear to fare more poorly than men.

DSM-5 Criteria for Neurocognitive Disorder Due to TBI

• The criteria are met for major or mild neurocognitive disorder.
• There is evidence of a traumatic brain injury—that is, an impact to the head or other mechanisms of rapid movement or displacement of the brain within the skull, with one or more of the following:
  • loss of consciousness.
  • post-traumatic amnesia.
  • disorientation and confusion.
  • neurological signs (e.g., neuroimaging demonstrating injury, new onset of seizures, a marked worsening of a preexisting seizure disorder, visual field cuts, anosmia, or hemiparesis).
• The neurocognitive disorder presents immediately after the occurrence of the TBI or immediately after recovery of consciousness and persists past the acute post-injury period.

The presentation of symptoms varies among individuals and depends largely on the location of the injury and the intensity of the trauma. Furthermore, the effects of TBI can be temporary or permeant. Symptoms generally range from headaches, disorientation, confusion, irritability, fatigue, and poor concentration as well as emotional and behavioral changes. More severe injuries can result in more significant neurological symptoms such as seizures, paralysis, and visual disturbances (APA, 2013).

The most common type of TBI is a concussion. A concussion occurs when there is a significant blow to the head, followed by changes in brain functioning. It often causes immediate disorientation or loss of consciousness, along with headaches, dizziness, nausea, and sensitivity to light (Alla, Sullivan, & McCrory, 2012). While symptoms of a concussion are usually temporary, there can be more permanent damage due to repeated concussions, particularly if they are within close time periods. The media has brought considerable attention to this with the recent discussions of chronic traumatic encephalopathy (CTE) which is a progressive, degenerative condition due to repeated head trauma. Chronic traumatic encephalopathy (CTE) is a distinctive tau-protein associated neurodegenerative disease. There has been a rise of chronic traumatic encephalopathy (CTE) diagnosis in athletes, especially American football players, as well as in military veterans in combat settings. Although chronic traumatic encephalopathy (CTE) has been publicly recognized relatively recently, it was first described as “punch drunk” syndrome in a classic article by Martland et al.  The report was focused on a number of boxers who had suffered repetitive head blows throughout their careers and were presented with both psychiatric symptoms as well as severe memory and neurocognitive deficits that were analogous to typical dementia patients. In addition to the neurological symptoms, psychological symptoms such as depression and poor impulse control have been observed in individuals with CTE. Individuals with CTE also appear to be at greater risk for development of dementia (McKee et al., 2013).

Prevention is another key strategy that needs to be implemented in various sports and military settings. Providing education for safe practice techniques, such as safe tackling and hitting, and providing ready access to full neuropsychiatric assessment by team physicians could have measurable benefits. The combination of advanced research techniques including neuroimaging, as well as increasing public awareness of CTE, offers promising vistas for research advancement.