Localizing Neurological Lesions

Copyright 2002 by John Tennison, MD



Lesion Location



Cerebral Cortex

Sensory/Motor Deficits contralateral to lesion.  Unlike Internal Capsule lesion, can have higher-level deficit, like aphasia, agnosia, or apraxia.

Lesions here do not result in crossed deficits as seen in brain stem and spinal lesions.

Internal Capsule

Sensory/Motor Deficits contralateral to lesion.

Lesions here do not result in crossed deficits as seen in brain stem and spinal lesions.


Motor Problems:  awkward intentional movements


Basal Ganglia

Motor Problems:  meaningless, unintentional, unexpected movements


Brain Stem


Contralateral Upper Motor Neuron Paralysis.  Contralateral proprioceptive and pain-temperature loss below the head.  Ipsilateral cranial nerve deficits. 

If cranial nerve involved, then lesion is above foramen magnum. 

Spinal Cord


Ipsilateral paralysis and proprioceptive loss.  Contralateral pain-temperature loss below level of lesion.

Radicular pain suggests lesion is below the foramen magnum.

Spinal Nerve Root

Usually more than 1 root severed will result in motor/sensory deficits in the pattern of 1 or more dermatomes, which have a repetitive banding pattern, unlike the seemingly random distribution of peripheral nerve areas.

If only 1 nerve severed, little if any motor/sensory defect because of overlap of distribution in adjacent roots.

Peripheral Nerve

Pattern of motor or sensory loss that is not in the form of a band characteristic of a dermatome, but instead is in an asymmetric, often discontinuous areas.

They have a patchy distribution since a peripheral nerve is a mixture of contributions from several nerve roots.



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