Read Full Text: Huntington Disease: Pathogenesis and Treatment (This article requires purchase, but we still thought it was important to be covered.)
Journal: Neurologic Clinics
Year Published: 2015
Ranked 28th on our 2015-2020 list of the 100 most influential OT-related articles
Huntington Disease is incredibly challenging for patients and their families. And treating patients with this disease will require your full skillset as an occupational therapy provider.
This week’s research review sheds some light on the way the brain changes in response to this disease. Not only does the brain deteriorate more profoundly than we recognized, the changes also begin much earlier than we thought.
There aren’t any evidence-based treatments that alter the progress of Huntington Disease, and there is not a cure at this point. But, the article does give an overview of available management options. As an OT, your care will be focused on symptom management and support—the value of which cannot be underestimated.
Let’s dive in.
What is Huntington Disease? (A high-level reminder)
Huntington Disease (HD) is an inherited disease that causes the progressive breakdown of nerve cells. Signs and symptoms usually develop between ages 35 and 44, and patients usually die within 15 to 20 years of diagnosis.
Typical clinical features include:
- Progressive motor disorder
- Progressive cognitive disturbance, culminating in dementia
- Psychiatric disturbances
The mutation is inherited in a dominant manner, meaning that children of patients with Huntington Disease have a 50% chance of inheriting the disorder.
What causes Huntington Disease?
HD is caused by a mutation on a single gene: the one that encodes the huntingtin protein. (Yes, the protein’s name is spelled differently than the disease!)
Although the exact function of this protein is unknown, we do know that healthy function is essential for normal development before birth.
In adults, the protein is found in many of the body’s tissues, and it appears particularly active in certain parts of the brain. So, we suspect that it plays a role in healthy cell function—we just don’t know exactly what that role is. (Here is the best explanation I found of this protein’s function.)
For reasons we are still trying to understand, when this single gene mutates like it does in HD, its protein becomes toxic. The eventual result is cell dysfunction and death.
What parts of the brain are most affected?
The striatum is traditionally considered to be the part of the brain that shows the most dysfunction early in the disease course.
This structure is interesting because it seems to play a critical role in both our motor system and our reward system.
I think it’s worth noting some other disorders that cause damage to the same part of the brain. As an OT, I think you’ll recognize some similarities in symptomatology:
- Parkinson’s Disease
- Addiction
- Bipolar disorder
- Autism spectrum disorder
- Depression
- Obsessive compulsive disorder
Understanding the affected area of the brain helped me appreciate the clinical features of HD, which we’ll look at now:
The clinical features of HD that OTs need to understand
There is a wide range of how HD presents, but there is also an overarching pattern, which involves 3 main clinical features.
1. Motor disorder
Chorea is one of the most recognizable features of HD. It is a movement disorder which involves involuntary, unpredictable muscle movement. Here’s a video (with no sound) of what chorea can look like:
Although chorea is often associated with HD, it is only one of many motor dysfunctions seen in patients with HD. Other movement abnormalities include:
- Abnormal saccadic eye movements
- Ataxia of speech, limbs, and gait
- Dystonia
- Bradykinesia
Falls and related injuries can become increasingly common as the disease progresses. Progressive motor failure is a major factor in life-ending complications.
2. Cognitive disorder
By the time a diagnosis is made, most patients present with cognitive impairment. Initial difficulties may include:
- Multi-tasking
- Focus
- Short-term memory
- Learning new skills
- Verbal fluency
Over the course of several years, cognitive impairment will progress to frank dementia.
It is extremely important to note that many patients with HD show better retention of episodic memory and language function than patients with Alzheimers-related dementia.
3. Psychiatric disorder
Psychiatric features and their severity vary greatly, but the article cites these as potentially the “most vexing.” Common features include:
- Depression
- Obsessive-compulsive behaviors
- Apathy
- Outbursts
- Personality changes
Research is indicating that damage is more widespread, and manifests earlier, than previously realized
So, we know that the striatum is particularly susceptible to mutant huntingtin proteins, which leads to some of the most recognizable symptoms we mentioned above. This has been understood for a long time.
But, remember how the huntingin protein is found throughout the body? We are just beginning to understand the systemic damage that the mutant protein causes. Global deterioration of the white matter in the brain appears to begin well before motor symptoms appear. Systemic changes (possibly affecting metabolism) may also account for symptoms like weight loss, which often appears in the pre-manifest phase.
Management
HD has no cure. And, no known therapy slows the rate of decline. Symptoms, however, can be treated and managed to ensure the highest quality of life possible for these patients and their families.
A quick note on pharmacological management
HD symptoms respond variably to medication. In general, psych symptoms are the most responsive to pharmacological treatment. Among the motor symptoms, chorea is the most responsive to medication. Cognitive symptoms are the least responsive to this type of treatment.
Nonpharmacological management (that’s you)
Multidisciplinary care is a critical component of HD management. As an OT, you’ll likely be part of a care team that includes:
- Primary care providers
- Neurologists
- Psychiatrists
- Geneticists
- PTs and SLPs
- Social workers and counselors
Some of the interventions shared in the article included:
- Gait assistive devices
- Home safety improvements (e.g. hazard removal, grab bars, and shower chairs)
- Evaluation of dysarthria and dysphagia
- Minimization of distractions at mealtime for safe swallowing
- Dietary consultations and possible use of high-calorie supplements
- Structured daily schedules
- Regular routines and cues
- Daytime respite care
- Family support that includes considerations for finances and other interpersonal and social stresses
As clinicians, we need to take special care to listen to and focus on the needs of each individual and family with whom we work. The authors emphasize that, even in advanced stages of HD, you should assume that a patient’s recognition and comprehension are preserved. Motor dysfunction related to speech can make patients appear more cognitively impaired than they really are.
Takeaways for OT practitioners
1. Even when referred for a single issue, we need to be aware of the big picture.
A patient with HD will probably be on your caseload for a specific issue, such as a home safety evaluation. But, it is extremely important that you are aware of the course of this disease, as well as the various hurdles the patient and family are navigating. There are no pat-answers to the challenges these patients and their families face, so you need to really listen to their concerns and address what they hope to gain from therapy.
Because of your experience in working with similar conditions, it is also important to speak up if you note additional challenges the team could be working to meet.
2. The increased knowledge of pre-manifest symptoms is an exciting trend we are seeing in the Club—it provides hope for better treatments in the future for some of the most difficult conditions on our caseload.
While the information in this article about pre-manifest symptoms may not have immediate implication for the patients currently on your caseload, it is important to know this trend: our understanding of pre-manifest symptoms (and testing) is improving, and may give us earlier indicators of the disease course. We also saw this in psychosis research. And, as OTs, we should be advocating to be involved in the disease process as early as possible, especially in the case of HD, so patients can be making decisions about what is meaningful to them, while they retain their full decision-making capacity.
Here’s the full APA citation for this article:
Dayalu, P., & Albin, R. L. (2015). Huntington Disease. Neurologic Clinics, 33(1), 101-114. doi:10.1016/j.ncl.2014.09.003