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4 - Sensory abnormality

from PART I - CLINICAL MANIFESTATIONS

Published online by Cambridge University Press:  17 May 2010

Jong Sung Kim
Affiliation:
Asan Medical Center, Seoul, South Korea
Julien Bogousslavsky
Affiliation:
Université de Lausanne, Switzerland
Louis R. Caplan
Affiliation:
Harvard Medical School
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Summary

Functional anatomy of somatosensory system

Functional anatomy of the sensory system is briefly discussed here. For further details, readers are referred to previous literature (Woolsey, 1958; Martin & Jessell, 1991; Parent, 1996; Kim, 1998a). There are two functionally and anatomically distinct sensory pathways, the medial lemniscal system and the spinothalamic system (Fig. 4.1). The medial lemniscal system subserves proprioception, vibration, tactile discrimination, and some touch sensations. These fibres ascend at the posterior column of the spinal cord up to the caudal medulla where they synapse on the dorsal column nuclei neurons (nuclei of Goll and Burdach). They then decussate as the internal arcuate fibres and ascend through the opposite medial lemniscus, which is located at the medial portion of the medulla oblongata. The spinothalamic system fibres are responsible for pain and temperature sensations. The peripheral fibres, after entering the dorsal root entry zone, ascend a few segments at Lissauer's tract and then synapse at the dorsal horn. From there, some fibres ascend ipsilaterally, but the majority of the fibres cross the midline in the white commissure and ascend toward the medulla. In the brainstem, the spinothalamic tract is located at the dorso-lateral tegmentum. Some of the spinothalamic fibres are also projected to reticular formations.

The facial (trigeminal) sensations are conveyed to the brainstem through the trigeminal nerves which enter the lateral pons. The fibres carrying touch and tactile discrimination synapse at the principal trigeminal nucleus located in the lateral pons. The secondary fibres (quintothalamic fibres) cross the midline and ascend to the thalamus. The fibres subserving pain and thermal sensations do not synapse at the principal sensory nucleus.

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Stroke Syndromes , pp. 34 - 47
Publisher: Cambridge University Press
Print publication year: 2001

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