PHYSICAL EXAMINATION

LABORATORY STUDIES

DIAGNOSIS

Parkinson’s disease

PATHOPHYSIOLOGY OF KEY SYMPTOMS

The patient’s primary symptoms revolve around movement. Whereas a decline in balance and coordination are part of the normal aging process, rapid deterioration of movements potentially represents a disturbance in the cerebrum, cerebellum, or basal ganglia.

The basal ganglia are a group of interconnected nuclei that modulate movement (Fig. 44-1). The striatum consists of γ-aminobutyric acid (GABA)ergic neurons that innervate the globus pallidus and the pars reticularis of the substantia nigra. Damage to the striatum causes Huntington’s disease. The major output of the substantia nigra is through dopaminergic neurons to the striatum. Damage to the neurons of the substantia nigra causes Parkinson’s disease. The globus pallidus projects to the thalamus and subthalamic nuclei using GABA as a neurotransmitter. Damage to the globus pallidus causes Tourette’s syndrome. The subthalamic nucleus uses glutamate as a neurotransmitter to stimulate the internal globus pallidus. Damage to the subthalamic nucleus results in hemiballismus.

FIGURE 44–1 Components of the basal ganglia and other closely associated brain regions. The main components of the basal ganglia are the caudate, putamen, globus pallidus, and substantia nigra pars reticulata. The motor loop of the basal ganglia connects with motor areas in the frontal cortex, the ventroanterior and ventrolateral (VA and VL) thalamic nuclei, and the superior colliculus. Input from the substantia nigra pars compacta is critical for normal basal ganglia function.