Huntington’s disease is a dominant autosomal inherited genetic disorder, meaning that the child of any parent with Huntington’s disease has a 50% chance of inheriting the disorder. The mutation that causes Huntington’s disease is a CAG repeat extension in the HTT gene on chromosome 4. If someone is born with a repeat number of 40 or higher, an individual will develop Huntington’s disease, typically around the age of 40 with an average life expectancy of 17-20 years after onset. In about 10% of cases, onset occurs before the age of 21, and is referred to as Juvenile Huntington’s disease. There are several key differences between adult and juvenile onset Huntington’s disease, including symptom presentation and life expectancy; JHD patients present with behavioral changes, muscle stiffness, clumsiness, decline of mental ability, difficulty with speech and swallowing, and bradykinesia (slowness of movement). Those with JHD also tend to have a CAG repeat number above 60 and a family history of early onset. JHD also progresses more quickly than adult onset HD, and life expectancy after diagnosis is on average 10 years(1). More information about Juvenile Huntington’s disease can be found here.
Treatment for JHD, much like HD, is limited to symptom management, and in many cases the implications of patients’ neuropsychiatric symptoms, such as impulse control, agitation, aggression, and obsessive behaviors, make it difficult for the patients to engage with in occupational activities such as therapy groups, family visits, and social interactions. Sensory modulation is the neurological function through which the body receives and processes incoming stimuli — smells, sight, sounds, taste, and touch. With this information, individuals can self-regulate and respond appropriately to their environment. Sensory modulation dysfunction (SMD) is when a person has difficulty processing sensory input, which leads to sensitivity as well as changes in arousal and emotional reactivity to an experience. This abnormal processing has been observed in JHD patients, suggesting that they may experience sensory input differently than non-affected individuals, and therefore be more likely to experience SMD. The ways in which a JHD patient may respond to sensory stimuli is therefore different from how one might expect. For example, this could manifest as being under reactive to touch, which may result in a person layering their clothing excessively and intruding on the personal space of others. It could also result in over reactivity to visual processing, leading to complaints of a messy environment and rearrangement of their surroundings.
In two case studies at the University of Melbourne, sensory modulation intervention strategies (SMIS) were used in order to reduce the prevalence of neuropsychiatric symptoms in two patients diagnosed with juvenile Huntington’s disease. The aim of these case studies was to explore the potential for SMIS in helping combat the consequences of sensory modulatory dysfunction in order to allow for JHD patients to engage in a wider range of occupational activities.
Names changed for privacy
The first case study was a 22-year-old female, Carrie-Anne, who had been diagnosed with JHD at the age of 16 and was living in a supportive care community. Her impulsive verbal and physical aggression had shown minimal response to medications or other behavior strategies. Due to these symptoms, she had restricted interactions with others and limited access to the community. Carrie-Anne’s sensory assessment showed that she had a lowered understanding of her sensory sensitivities and was unable to control her sensation satisfying behaviors; this led to physical aggression. Prior to physical aggression Carrie-Anne would show precursors such as pacing, voicing hunger, verbal aggression, and intrusiveness. She would also seek out activities that satisfied her sensory compulsions, such as dressing in layered clothing, standing close to people, and vocalizing hunger as well as dissatisfaction with the flavor of her food. The sensory modulation intervention implemented for Carrie-Anne used strategies that she indicated she preferred — a weighted blanket and vibrating massager, as well as added condiments to Carrie-Anne’s food to enhance the taste experience as recommended by her occupational therapist. Carrie-Anne was able to successfully use these SMI strategies in order to regulate her reaction and emotional stability. Instead of pacing or becoming verbally aggressive, Carrie-Anne would rest with her weighted blanket, after which she would occasionally resume pacing, but the risk of escalation to physical aggression was dramatically diminished. In addition, after implementation of these sensory modulation intervention strategies, Carrie-Anne was able to more frequently engage in meaningful activities and with the community.
The second case study is of a 31-year-old male, Christopher, who had exhibited symptoms of JHD since his late teens but was not formally diagnosed until he was 29. This happens most often because many of the symptoms of JHD, such as behavioral changes, can be confused with normal adolescence or a psychiatric disorder. Christopher was living in a supported community but frequently needed emergency services to address his risk of aggression despite medication. A sensory assessment showed that Christopher was over-reactive to auditory processing; essentially he was sensitive to sound. This sensitivity manifested itself in verbal and physical aggression when the television was on or if another resident was speaking. Before SMIS, Christopher would be given medication and removed to his own room to avoid any risk to others. The chosen SMIS for Christopher consisted of those that he had an affinity for. This included a click-clack ball (a hollow, soft, apple sized ball with hard objects inside), a hand held vibrating massager, and a weighted blanket. Upon employment of these strategies in situations in which Christopher would usually become agitated, Christopher’s complaints and involuntary movements would lessen. In addition, the risk of him escalating to verbal or physical abuse was drastically lowered. This allowed Christopher to stay in communal areas and interact with other residents in a group setting.
In conclusion, these two case studies indicate a potential role for sensory modulation intervention strategies (SMIS) as an effective occupational therapy tool for those suffering from neuropsychiatric symptoms of JHD. Both patients assessed had previously been unable to engage in community spaces due to their increased amount of neuropsychiatric disturbance. However, with SMIS, both Carrie Anne and Christopher were able to participate in meaningful activities such as group therapy and events. As these case studies only discuss two patients, the effectiveness of SMIS cannot be generalized as an appropriate strategy for all JHD patients. However, with further research and practice, this strategy may be a valuable tool for improving the quality of life of JHD patients.
(1) Brown, Anahita, and Caroline Fisher. “Optimising occupational performance through sensory modulation interventions: Case reports of two young adults diagnosed with juvenile Huntington’s disease.” British Journal of Occupational Therapy (2015): 0308022615569249.