PT Management Huntington's Disease Flashcards
HD definition:
“Huntington disease (HD) is a progressive hereditary disorder characterized by abnormalities of movement, personality disturbances, and dementia. Known also as Huntington chorea, it is most often associated with choreic movement that is brief, purposeless, involuntary, and random.”
What chromosome is the mutation for HD on?
chromosome 4–> increases the number of CAG repeats
–> gene that produces a protein called huntington which causes neuronal degeneration and eventual neuronal death
HD pathology disrupts complex balance of excitation and inhibition between the thalamus and the BG for smooth, coordinated movement–> disrupts normal pathway between indirect and direct pathway
Life expectancy after dx:
15-20 years
Age of onset:
-usually after age 30 (65%)
-late onset: after age 50 –> best prognosis with potential to survive into 8th decade
-juvenile onset: <20 years (10% of cases)
What kind of trait is Huntington’s Disease?
autosomal dominant–> if you inherit the genetic mutation you will develop the disease
50/50 chance of getting the disease if the parent has the genetic mutation
cytosine, adenine, and guanine DNA nucleotides are repeated more than normal –> number of repeats related to amount of disease burden
Triad of Huntington’s Disease
neuropsychiatric symptoms
progressive movement disorder
eventual dementia
CAG repeats and their significance
normal: <26
27-35: will not develop HD but will pass risk to their children
36-39: some, but not all, will develop HD and will pass the risk to their children
>40: all will develop HD and their children will have a 50% risk
>50 repeats: juvenile onset
pre symptomatic HD (pre-manifest)
defined as the period before the onset of cognitive, motor or behavioral symptoms
-might have HD but haven’t developed symptoms yet
prodromal phase of HD
defined as the period just prior to
diagnosis, where cognitive, motor or behavioral
symptoms begin but do not yet meet the criteria
for HD diagnosis
** some symptoms are present but not to extent of diagnosis
Criteria for HD diagnosis:
CLINICAL SIGNS
-cognitive –> before motor
-psychiatric –> before motor
-motor
-positive family history
-imaging (not used diagnostically)
—MRI and CT: loss of neurons in striatum (BG)
—PET and fMRI can detect the disease 11 years prior to symptoms
-genetic testing
Natural History of HD
at first–> there is a lack of inhibition of the thalamus–> leads to an increase in movement and chorea (INDIRECT PATHWAY)
then, movement gradually begins to decrease as the disease progresses (DIRECT PATHWAY)
-increase rigidity and bradykinesia as there is a steady decline in the volume of various brain areas: cortical grey matter, globus pallidus, cortical white matter, striatal volume
The degree of motor impairment usually exceeds that of ___, _____, impairments
cognitive and chorea
What brain areas are the most affected in HD
the cerebral cortex and the BG
decrease neurons from striatum to substantia nigra
psychiatric abnormalities are likely due to striatal-frontal lobe circuitry damage
COGNITIVE/BEHAVIORAL SYMPTOMS HD
- Decreased judgment
- Changes in social behavior
- Loss of memory
- Depression
- Hostility
- Apathy
- Decrease in IQ
- Deterioration of speech and
writing
MOTOR SYMPTOMS HD
choreiform movements
apraxia
cerebellar signs: ataxic gait, decreased force control
-motor impersistence: inability to maintain constant voluntary contraction
dystonia: arm elevation in gait, lateral flexion, foot PF/INV
—Dystonia is a movement disorder that causes the muscles to contract involuntarily. This can cause repetitive or twisting movements.
oculomotor abnormalities
–saccades
-saccadic intrusions with smooth pursuits
-visual distractibility
