Point 5


Intro

Pathway

Deficit

Note

Summary

Overview

Problems


Contents

Anatomy

 

 

Due to its small size, lesions restricted to the accessory cuneate nucleus are rare. Understanding the laterality (which side) and specific deficits resulting from a lesion of the accessory cuneate requires knowing something about CEREBELLAR functions and connections. While this important topic is covered later in this course, we need to do some limited spade work right now to get you prepared for those lectures, and to also let you problem solve on questions regarding lesions of brain stem areas that either project to the cerebellum (like the accessory cuneate nucleus, inferior olive and pontine grey [the latter two will be discussed further up the brain stem]) or contain axons leaving the cerebellum (superior cerebellar peduncle).

The cerebellum is involved in motor coordination. Unlike the cerebrum (i.e., cerebral cortex; cells of origin of the corticospinal tract), the cerebellum has no major projections to the spinal cord, but instead regulates movement indirectly by projecting to areas of the brain that do project upon the spinal cord. Lesions of the cerebellum lead to defects in the coordination of movements, but NOT paresis or paralysis. Such cerebellar defects involve errors in the rate, range or direction of voluntary movements. Disturbances following cerebellar lesions are known by a variety of terms such as nystagmus, ataxia, hypotonia, dysmetria, past pointing, rebound, dysdiadochokinesia, asynergy, intention tremor and decomposition of movement (WHEY!). RIGHT NOW, LET'S JUST CALL THESE DISTURBANCES==INCOORDINATION AND REMEMBER THAT INCOORDINATION RESULTS FROM LESIONS OF THE CEREBELLUM OR ITS INPUTS (ACCESSORY CUNEATE NUC.) OR OUTPUTS.

In addition to knowing that lesions of the cerebellum and its inputs and outputs result in incoordination, we need to know what part of the body is affected (arm, leg) and the laterality (IPSI. or CONTRA.). The important point now is that you understand that one side of the cerebellum controls the SAME OR IPSILATERAL SIDE OF THE BODY.