This page will attempt to describe some of the clinically important anatomical relationships between various regions of the brain, spinal cord and peripheral nervous system. When deemed appropriate, selected tracts will be shown and methods to ascertain the status of each of these will be described, with particular emphasis on the proper neuroexamination technique(s). This project is already started and publication of portions of it will appear here over time.

Track and Pathway Map...Sensory.......Motor.....Mentation...

Tracts and Pathways Map:

Appreciating the relative arrangement of sensory and motor pathways within the spinal cord and brain are of fundamental importance if one is to understand the how to localize sources of dysfunction in a way that is not simply rote memory, but totally rational. This section will include pictures and descriptors that accentuate the clincally important anatomical areas. Please be patient as preparing this material is somewhat time-labor intensive. A preliminary diagramatic representation of major tracts is provided here...

Thanks,

Chick

lesion site vs clinical problem...

Here is an interactive way to learn tracts and pathways...

Place the cursor over the spine cross section, then manipulate the result using the buttons above and below that image...

Sensory:

Proprioception:

Proprioception is the awareness of body position. Body position is perceived at conscious (CP) and unconscious (UCP) levels.

Conscious proprioception(CP):

Sensory information from from receptors in limbs and trunk is carried by perifpheral nerves then the spinal cord (via faciculus cuneatus and faciculus gracillus) to the brainstem where it crosses over to the contralateral cerebral cortex; here precise information about the position and orientation of limbs and trunk is perceived and organized. (for schematic of this, see above)

This information is utilized to facilitate complex motor activity, e.g. running/catching a frisbee, fighting

Defects anywhere along the pathway are manifest as stumbling, knuckling; however, the routine gait and posture may be normal (depending on status of UCP...see below)

Unconcious Proprioception(UCP):

Sensory information from receptors in the limbs and trunk are transmitted via peripheral nerves to the spinocerebellar tracts where the information terminates on the ipsolateral cerebellum

This information is utilized to coordinate basic posturing during sitting, standing and simple gait activities

Defects anywhere along the pathway may be manifest as postural deficits, ataxia

Pain:

Pain includes thermal, bone-crushing pressure, superficial irritation (e.g. pinprick)

Painful stimulation of peripheral pain receptors is carried by peripheral nerves impulses to the spinal cord. Impulses are transmitted via spinothalamic tracts in the cord to the contralateral sensory cortex where pain is recognized and to the RAAS (ARAS...the ascending reticular activating system) which is concerned with mentation /arousal. The latter also diffusely signals generalized cortical arousal . (For a schematic representation, see above)

Defects anywhere along this pathway are manifest as hypoaesthesia/ anesthesis

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