basal ganglia

Question 0

huntingtons disease

Answer 0

is an autosomal dominant condition that is characterised by:
- progressive, choreiform movements, psychiatric distubrances and death

it is associated with atrophy of the striatum (caudate and putamen), in particular the caudate, in late stages of the disease there is loss of the globus pallidus also - and both direct and indirect pathways are affected

atrophy of the striatum causes the ventricles to appear larger on MRI and CT

the genetic defect is a CAG repeat - the greater the number of repeats the faster the disease onset (anticipation through generations). the trinucleotide repeat creates a toxic Huntingtin protein, which is suggested to cause oxidative stress.

the treatments are limited and include dopamine depleting agents and supportive care for psychiatric manifestations

most die from dementia

Question 1

parkinsons disease

Answer 1

is a sporadic disorder of unknown aetiology

it is associated with a resting tremour, bradykinesia, and cogwheel rigidity with an insteady gait. persons have slow movements which are difficult to initiate and therefore is is classed as a hypokinetic disorder.

it is characterised with a loss of the substantia nigra pars compacta nuclei within the basal ganglia

pathologically there may be cytoplasmic inclusion such as Lewy bodies

there are some rare famililal cases, but have been suggested that fungicides, herbicides and pesticides may have a role in aetiology

diagnosis is confirmed when there is improvement with levodopa

carbidopa is the mainstay treatment as it prevents dopamine conversion outside the CNS

Question 2

hemihallibismus

Answer 2

flapping movements which have no purpose, generally associated with sub thalamic nuclei degeneration

Question 3

the direct pathway….

Answer 3

allows for movement to occur

Question 4

the indirect pathway

Answer 4

does not allow movement to occur

Question 5

the substantia nigra has two parts

Answer 5

substantia nigra pars compacta - which is inhibitory in the indirect pathway and degenerates in PD, yet excitatory in the direct pathway

substantia nigra pars reticulata - which is inhibitory and activates the thalamus

both are dopaminergic i.e. produce dopamine - dopamine can be both an excitatory or inhibitory neurotransmitter, depending on context

Question 6

glutamate

Answer 6

is an excitatory neurotransmitter which is produced by the cortex, the STN (subthalamic nucleus) and the thalamus

Question 7

Acetylcholine is produced where in the basal ganglia

Answer 7

within the striatum (between the putamen and caudate) by aspiny neurons

anticholinergics working this way may help reduce activation of indirect pathway by Ach in parkinsons disease

Question 8

GABA, Substance P and enkepahlin are all:

Answer 8

inhibitory neurotransmitters

Question 9

what is dyskinesia

Answer 9

abnormal movements

Question 10

tardive dyskinesia

Answer 10

is a form of dyskinesia akin to parkinsons which is seen in persons who have been on chronic antipsychotics and antiemetics which antagonise dopamine

neuroleptics are now used as an alternative