Basal Nuclei (Ganglia)

Abnormal involuntary movements (AIMs) should be viewed as clinical signs with many causes. For example, parkinsonism may be the clinical manifestation of a variety of conditions with different or unclear etiologies. Defining the broad category of the movement disorder in a given patient precedes the classic approach to neurologic diagnosis: localizing the lesion and determining the etiology of the condition. A careful history with particular attention to family background, pregnancy, labor and delivery, early developmental milestones, trauma, infections, medical and psychiatric comorbidities, and use of illicit drugs and medications, especially neuroleptics, are particularly important when first evaluating a patient with abnormal involuntary movements and may suggest the underlying cause. A detailed general medical examination with emphasis on eye movements, presence of Kayser-Fleischer rings (suggesting Wilson disease), and funduscopic examination looking for retinopathy and optic nerve abnormalities (papillitis, papilledema, or optic nerve atrophy suggesting demyelinating diseases, metabolic disorders, or mitochondrial cytopathies); organomegaly (betraying metabolic or storage diseases); and skin discolorations or deposits (defining phakomatosis, xeroderma pigmentosum, vitaminosis, gastrointestinal disease, malabsorption, calcinosis, or cholesterol deposits, especially at the muscle tendons) may prove rewarding. Searching for additional clues, with a carefully performed neurologic examination, will help in the understanding of the patient’s condition.

Once the abnormal movements have been classified, and the neurologic accompaniments documented and placed in context, the cause may become apparent and proper ancillary testing may be undertaken.

ANATOMY OF THE BASAL GANGLIA AND RELATED STRUCTURES

Anatomically, the basal ganglia constitute a complex circuitry that includes neurons of the caudate nucleus, putamen, subthalamic nucleus (STN) globus pallidus, and substantia nigra (SN). The output of the basal ganglia is directed at the motor thalamus (and from there to the frontal cortex) and the pedunculopontine nucleus (PPN).

Only gold members can continue reading. Log In or Register to continue