9 topics with a brief review: definitions, key facts, and classroom questions.
Movement is the basis of vital activity, and its disorders are one of the most common reasons for visiting a neurologist. In this chapter, we analyze in detail the anatomy and pathology of the motor system: from the basic segmental-reflex apparatus of the spinal cord to complex cortico-muscular (pyramidal) tracts.
A separate section is devoted to coordination and extrapyramidal regulation. You will learn to recognize parkinsonism syndrome and various types of hyperkinesia, distinguish between types of ataxia, and analyze specific gait disorders. The section concludes with an analysis of apraxia, a disorder of complex purposeful actions in which muscle strength remains intact.
During practical classes and exams, differential diagnosis of central and peripheral paralysis (signs of cortico-muscular pathway lesions) as well as clinical markers of parkinsonism are tested most rigorously. Pay special attention to topic localization: it is precisely this that allows you to accurately determine the level of the nervous system lesion based on the nature of the gait disorder or the type of hyperkinesia.
What structures form the upper motor neuron of the cortico-muscular pathway?
The upper motor neuron (pyramidal tract) originates from the precentral gyrus, the premotor area of the frontal lobe, and partially the postcentral gyrus. Its axons pass through the corona radiata, the posterior limb of the internal capsule, and the brainstem to the spinal cord.
Why do the hands and feet suffer more than trunk muscles in central paresis?
The trunk and proximal muscles have bilateral cortical innervation thanks to the anterior uncrossed pathway. Distal limb segments are innervated predominantly unilaterally (via the crossed lateral tract), making it harder to compensate for their damage.
How to detect latent paresis in the upper extremities?
The patient is asked to extend their arms forward in a supinated position and close their eyes (Barré's test). If central paresis is present, the affected arm will begin to pronate and drop.
How to properly elicit superficial abdominal reflexes?
It is necessary to apply a light stroking stimulus with the blunt end of a neurological hammer. For the upper reflex, the line is drawn along the costal margin; for the middle reflex, horizontally at the umbilical level; for the lower reflex, parallel to the inguinal fold.
What is the difference between synkinesias and fasciculations?
Synkinesias are associated involuntary movements of an entire limb when attempting to perform a voluntary action, which is a sign of central paresis. Fasciculations are local twitchings of muscle bundles indicating a lower motor neuron lesion (e.g., anterior horns of the spinal cord).
How does plastic tone in rigidity differ from spastic tone?
With plastic tone, muscle resistance is felt evenly throughout the passive movement (the "lead-pipe" phenomenon), muscle strength is preserved, and pathological reflexes are absent. With spastic tone, resistance increases only at the beginning of muscle stretch.
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