MRI scan in a 57 year old patient presenting with movement disorder. A coronal MRI section of the brain shows marked enlargement of the lateral ventricles, this is caused by atrophy (atrophy is a wasting away or shrinkage usually as a result of the degeneration of cells) of the caudate nucleus and putamen. Findings: Classic features consistent with clinical diagnosis of Huntintgon’s Disease.
Coronal MRI of a normal brain. The Caudate Nucleus and the putamen are marked on the scan to compare with the atrophied features in Image 1 that are typical of Huntington’s Disease. The Caudate nucleus are one of the nuclei that make up the basal ganglia together with the putamen. The putamen is a large, rounded structure located at the base of the forebrain and involved in aiding movement of the limbs. The basal ganglia act as a cohesive functional unit and are associated with voluntary motor control, learning, routine behaviours, cognitive and emotional function and eye movements. To demonstrate the structure and function of this part of the brain helps in the understanding of the symptoms of Huntington’s Disease.
Huntington’s disease is a hereditary degenerative brain disorder that damages certain nerve cells of the brain, which in turn cause degeneration, or atrophy (shrinkage) of parts of the brain and leads to serious cognitive decline affecting both behaviour and movements.(1) The disease is an autosomal dominant condition, which means that it can be inherited if only one parent carries the defective gene. Although babies are born with the disease, the symptoms usually become apparent between the ages of 35 and 44 years old, but the disease onset can start at any age,(2) if symptoms begin before the age of 20 years old, the disease becomes known as ‘Juvenile Huntington’s Disease’. There is a wide variation in the onset and progression of the disease including the extent of behavioural and cognitive symptoms, although the physical symptoms are eventually similar in most patients.(3)
The human brain: Comparison of a normal brain and changes due to Huntington’s Disease. The bottom image of the brain is normal. The top image of the structure of the brain, in comparison, clearly shows the large degeneration in the basal ganlia region in a patient with Huntington’s Disease.
The early physical symptoms of Huntington’s disease begin with minor motor abnormalities such as muscle twitching or restlessness, lack of coordination and slowed or abnormal eye movements.(4) The most characteristic initial symptom of the disease, as mentioned above, is ‘chorea’ which refers to random, involuntary, jerky or writhing movements of the arms or legs. As Huntington’s Disease progresses dystonia develops, which is characterized by a state of abnormal muscle tone resulting in muscular spasms and abnormal posture. Difficulties in chewing, swallowing and speech can also cause major problems.(5)
Cognitive skills related to reasoning, judgement and thinking are closely linked to behaviour. The early cognitive symptoms of Huntington’s Disease can include memory problems, difficulty with concentration and orientation, mood swings, such as apathy and aggression, and sometimes uninhibited behaviour. Because the disease is progressive, these cognitive and behavioural problems deteriorate over time and can ultimately result in dementia. Huntington’s disease is associated with a range of psychiatric disturbances that include affective disorders, psychosis and major depression. Interestingly the rate of depression was found as a precursor to the clinical onset of the disease.(6) The closer in proximity to the clinical onset of Huntington’s disease, the higher the rate of depression in patients.
1. Hammond, K; B Tatum (June 26, 2010). ‘The Behavioral Symptoms of Huntington’s Disease’. Huntington’s Outreach Project for Education, at Stanford. Retrieved August 4, 2014.
2,4,5. Walker FO (2007). ‘Huntington’s disease’. Lancet 369 (9557): 218–28. doi:10.1016/S0140-6736(07)60111-1. PMID 17240289.
3. Kremer B (2002). ‘Clinical neurology of Huntington’s disease’. In Bates G, Harper P, and Jones L. Huntington’s Disease – Third Edition. Oxford: Oxford University Press. pp. 28–53. ISBN 0-19-851060-8
6. Julien CL, Thompson JC, Wild S, et al. Psychiatric disorders in preclinical Huntington’s disease. Journal of Neurology, Neurosurgery, and Psychiatry 2007;78(9):939-943. doi:10.1136/jnnp.2006.103309.