LOCALIZATION OF LESIONS

One of the important aspects of evaluating any neurologic patient is to determine the location of the lesion. Luckily, the function of the nervous system is intimately tied to its structure. As such, when a function is lost, the structure involved is uncovered. Signs of neurologic disease can be divided into those representing diseases above the foramen magnum (head signs) and those below the foramen magnum (spinal cord signs). Head signs include seizures, head tilt, cranial nerve deficits, whole body and head tremors, and ataxia. Spinal cord signs include quadriparesis and paraparesis. The peripheral nervous system shows signs consistent with the distribution of the nerve involved. (See Table 1) Once the disease process is localized, the differential diagnosis can be made and the diagnostic approach determined.
 
 

Table 1. Neurologic Signs and Lesion Location.
Neurologic Sign		Location of Lesion
Change in Behavior or Personality		Cerebral Cortex, Thalamus, Hypothalamus
Seizures		Cerebral Cortex, Thalamus, Hypothalamus
Visual Dysfunction		Retina, Optic nerve, Visual pathways, Cerebral Cortex
Signs of Cranial Nerve Dysfunction
	Anisocoria	Sympathetic or Parasympathetic innervation to the eye
	Strabismus	CN III, CN IV, CN VI
	Dropped jaw	CN V
	Changed facial sensation	CN V
	Paralysis of eyelid, lip or ear	CN VII
	Dysphagia	CN IX, CN X
	Megaesophagus	CN X
	Laryngeal paralysis	CN X, CN XI
	Paralysis of tongue	CN XII
	Head tilt, circling, nystagmus	CN VIII (vestibular system)
	Deafness	CN VIII (auditory system)
Incoordination of the Head and Body		Cerebellum
Paraparesis or Paraplegia		TL Spinal Cord
Paralysis of one Limb		Peripheral nerve
Flaccid Anus, Tail and Bladder		Cauda Equina

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Last updated 27 August 2002