High-Yield Neuroanatomy 5e

Basal Nuclei and Extrapyramidal Motor System 125
GLU
Neocortex
GLU
Brain stem and
spinal cord
GLU
(Destruction results in Huntington’s disease)
Thalamus
GABA
GABA
GLU
GLU
ACh
Striatum
GABA/ENK
GABA/SP
Dopamine
GABA/SP
S. nigra
Compacta
Reticularis
(Destruction results in
Parkinson’s disease)
Subthalamic
nucleus
GLU
GABA
Globus
pallidus
(Lesions found here
in Wilson’s disease)
(Destruction results
in hemiballism)
(Lesions found here
in kernicterus)
Figure 16-6 Major neurotransmitters of the extrapyramidal motor system. Within the striatum, globus pallidus, and
pars reticularis of the substantia nigra (S. nigra), γ-aminobutyric acid (GABA) is the predominant neurotransmitter. GABA
may coexist in the same neuron with enkephalin (ENK) or substance P (SP). Dopamine-containing neurons are found in
the pars compacta of the substantia nigra. Acetylcholine (ACh) is found in the local circuit neurons of the striatum. The
subthalamic nucleus projects excitatory glutaminergic fibers to the globus pallidus. GLU, glutamate.
CASE 16-1
A 30-year-old man presents with dysarthria, dysphagia, stiffness, and slow ataxic gait. There is no history of
schizophrenia or depression and no family history of any neurodegenerative disease.
Relevant Physical Exam Findings
●
The patient scored a 20/26 on the mini-mental status exam. The patient showed increased tone in all
extremities, with normal strength.
Relevant Lab Findings
●
A generalized cerebral and cerebellar atrophy and a very small caudate nucleus were revealed on magnetic
resonance imaging scans.
Diagnosis
●
Huntington disease (chorea) is caused by a trinucleotide repeat in the gene coding for the Huntingtin
protein. It is characterized by abnormal body movements and lack of coordination but can also affect
mental abilities.