The Spinal Cord

Abstract

This chapter develops the anatomofunctional organization of the gray and white matters according to recent neurophysiological data particularly for analysis and rehabilitation of spinal lesions.

The gray matter includes:

• the central core characterized by a network organization of interneurons in charge of the basic motor and vegetative programmes essential for the locomotion and the survival of the individual,

• dorsal expansions responsible for treating pain and temperature information by a complex arrangement explaining pain by nociceptive excess and pain by deafferentation.

• ventral expansions including motoneurons organized in cellular islets whose actions are intended for skeletal musculature and functionally represent a final common pathway responsible for executing all motor orders of segmental reflex expression and of supraspinal origin that intervene on the strength and direction of movement and on the tone that accompanies movement.

The white matter features the passage of fibers from or to the cord, organized in descending and ascending tracts.

The dorsal column carries epicritic and kinesthetic information, the anterolateral funiculus conveys painful and thermal information, and spinocerebellar tracts occupy the lateral column. These ascending systems can be grouped into three systems, one for information, one for programmation, and a non-specific system for alertness, emotional, and vegetative states.

The descending pathways convey the motor orders that respond to conscious, finalized, voluntary, fine and idiokinetic gestures corresponding to pyramidal corticospinal tracts and non-pyramidal tracts that come from suprasegmental formations of the brain stem where cortical and cerebellar influences are relayed and can be grouped into a medial contingent for postural axial extensor tone and a posterolateral contingent that influences the tone of attitude which facilitates flexors of intermediate segments of the limbs. So, in the pathological situation different states of rigidity can be observed depending on the level of impairment creating by their imbalance, decerebration rigidity, or decortication rigidity.

The lesions of these different fascicules of white matter are responsable for sublesional syndromes observed in pathological situations and lesional syndromes reflects the involvement of gray matter.