Terminology and Description of Clinical Signs of Neurologic Disease (See Table 8.1)
Telencephalon (cerebrum, basal ganglia) and diencephalon (thalamus)
Changes in behavior
Changes in the level of consciousness
Dullness, obtundation
Stupor
Coma
Excitement, mania
Seizures (convulsions)
Narcolepsy
Vision disturbance
Blindness in both visual fields (amaurosis)
Blindness in the contralateral visual field (hemianopsia) Menace reflex deficit
Change in pupil size: small to pinpoint pupils Circling (toward the side of the lesion) Head turn (toward the side of the lesion) Gait usually normal Abnormal postural reactions (contralateral)
Decreased or absent conscious proprioception
Noticeable ataxia, paresis (weakness), and paralysis are uncommon
Abnormal spinal reflexes
Normal to increased (hyperreflexic) myotatic reflexes
Altered muscle tone
Normal to increased muscle tone (spasticity)
Urinary incontinence (upper motor neuron)
Tremors
Mesencephalon (midbrain)
Changes in the level of consciousness
Dullness (depression)
Stupor
Coma
Narcolepsy
Abnormal posture
Opisthotonos
Decerebrate posture
Abnormal visual or ocular function
Blindness in both visual fields (amaurosis)
Blindness in the contralateral visual field (hemianopsia) Change in pupil size
Small pupils in early, mild lesions
Dilated, nonresponsive pupils in severe lesions
Menace reflex deficit (ipsilateral)
Anisocoria (asymmetric lesions)
Circling (toward the side of the lesion—ipsiversive) Head turn (toward the side of the lesion—ipsiversive) Abnormalities of gait (usually contralateral to lesion) Decreased or absent conscious proprioception Ataxia
Paresis (weakness)
Paralysis
| ■ TABLE 8.1 | |
| Localization of Central Nervous S | ystem Lesions According to Major Signs Encountered |
| Sign or Problem Encountered | Lesion Location |
| Changes in Gait and Locomotion | |
| Ataxia | Spinocerebellar tracts, spinal cord, and brainstem; vestibular system; cerebellum |
| Conscious proprioceptive deficit | Fasciculus gracilis and fasciculus cuneatus and connections, spinal cord, brainstem, forebrain |
| Knuckling | Usually LMN, ventral horn gray matter, spinal cord; occasionally UMN, spinal cord, brainstem |
| Abduction or adduction | Spinocerebellar tracts, spinal cord, brainstem, cerebellum |
| Abnormal postural placement | Spinocerebellar tracts, spinal cord, and brainstem; gracilis and fasciculus cuneatus and connections, spinal cord and brain |
| Hypermetria | Cerebellum, cerebellar peduncles, spinocerebellar tracts |
| Circling, or falling to one side | Forebrain, vestibular nuclei and connections, cerebellum |
| Paraplegia | UMN, T2 to S2, or LMN, L3 to S2 |
| Hemiplegia | Ipsilateral brainstem or spinal cord, cranial to T3 |
| Changes in Sensorium and Behavior | |
| Coma or semicoma | ARAS; diffuse forebrain |
| Obtundation | ARAS; forebrain |
| Seizures | Forebrain |
| Head pressing, compulsive walking | Forebrain |
| Aggression or rage | Forebrain |
| Inappropriate sexuality | Forebrain |
| Hypothalamus | |
| Diabetes insipidus | Hypothalamus |
| Headshaking | Unknown, probably peripheral trigeminal neuralgia |
| Changes in Head Posture | |
| Stiff neck | Meninges, cervical spine |
| Head tilt | Vestibular nuclei and connections (medulla oblongata, cerebellum) |
| Head tremor | Cerebellum, basal ganglia |
| Opisthotonos | Cerebellum (rostral vermis), rostral brainstem, cerebrum, cranial nerve VIII |
| Cranial Nerve Dysfunction | |
| Blindness | Cerebral cortex, internal capsule, optic tracts, optic chiasm, optic nerve, eye |
| Anisocoria | Cervical spinal cord (tectotegmentospinal tract), cranial thoracic nerve roots, vagosympathetic trunk, midbrain (oculomotor nerve nucleus), cranial cervical ganglion, ciliary ganglion, oculomotor nerve, optic nerve |
| Mydriasis | Oculomotor nerve, midbrain, optic nerve, eye |
| Miosis | Vagosympathetic trunk, ciliary ganglia, tectum, brainstem, cervical spinal cord Facial nerve, vagosympathetic trunk, cranial cervical ganglion, midbrain, oculomotor nerve, cervical spinal cord (tectotegmentospinal tract) |
| Ptosis | |
| Strabismus | |
| Ventrolateral | Cerebellum, vestibular nucleus, oculomotor nerve |
| Dorsomedial | Trochlear nerve |
| Medial | Abducent nerve |
| Nystagmus | |
| Horizontal | Nerve VIII (peripheral) |
| Vertical or rotatory | Vestibular nuclei, peripheral vestibular receptor, cerebellum, vestibulocochlear nerve |
| Jaw drop | Trigeminal motor nucleus (pons), trigeminal nerve |
| Flaccid tongue | Hypoglossal nucleus (medulla oblongata), hypoglossal nerve, lingual muscle |
| Facial paralysis | Facial nucleus (medulla oblongata), facial nerve, facial muscles |
| Facial analgesia | Trigeminal nerve (sensory component), pons, forebrain |
| Dry eye | Cranial nerve VII before exiting petrous temporal bone |
| Changes in Reflexes | |
| Patellar | L3-L6 spinal cord, femoral nerve, quadriceps femoris muscle |
| Flexors (thoracic limbs) | C5-T2 spinal cord segments, radial, ulnar, musculocutaneous and median nerves, and innervated muscles |
| Flexors (pelvic limbs) | L6-S2 spinal cord segments (pelvic limbs); sciatic, peroneal, and tibial nerves; flexor muscles of the limbs |
| Triceps | C6-T1 spinal cord segments, radial nerve, triceps muscle |
| Cutaneous trunci | C8-T1 spinal cord segments, lateral thoracic nerve, white matter of thoracic spinal cord |
| Anal | S1-S5 sacral spinal cord segments, pudendal nerve |
| Cervicofacial | Dorsal columns of cervical spinal cord segments; facial nucleus (medulla oblongata), nerve, facial nucleus, muscles of ear; connections between cervical plexus and facial nerve |
| Dysuria (dribbling urine) | Spinal cord, S1-S5, sacral nerves, bladder wall |
ARAS, Ascending reticular activating system; LMN, lower motor neuron; UMN, upper motor neuron.
Abnormal spinal reflexes
Normal to increased (hyperreflexic) myotatic reflexes
Altered muscle tone
Spasticity
Urinary incontinence (upper motor neuron) Metencephalon (pons, cerebellum)
Abnormal posture
Head tilt
Decerebellate posture
Circling (usually away from side of lesion—paradoxical signs) Head turn (usually away from side of lesion—paradoxical signs) Nystagmus (variable—may be constant, positional, direction changing, or disconjugate and may occur in any direction) Abnormalities of gait
Ataxia
Dysmetria—typically, hypermetria
Abnormal spinal reflexes (occasional)
Normal to increased myotatic reflexes (hyperreflexia) Altered muscle tone
Normal to increased muscle tone on the opposite side of the body (contralateral spasticity)
Normal to decreased muscle tone on the same side of the body (ipsilateral hypotonus)
Urinary incontinence (upper motor neuron) (rare) Medulla oblongata
Changes in the level of consciousness
Dullness, obtundation
Abnormal posture
Head tilt (toward side of lesion—ipsiversive)
Circling (toward side of lesion—ipsiversive)
Head turn occasionally (toward side of lesion) Strabismus—variable
Nystagmus—spontaneous, abnormal (variable—may be constant, positional, direction changing, or disconjugate and may occur in any direction)
Dysphagia
Facial analgesia
Facial paresis or paralysis
Menace reflex deficit
Jaw weakness
Roaring, snoring, dysphonia
Tongue weakness, deviation, or paralysis
Abnormalities of gait—ipsilateral
Decreased or absent conscious proprioception Ataxia
Paresis (weakness)
Paralysis
Abnormal spinal reflexes
Normal to increased (hyperreflexic) myotatic reflexes
Altered muscle tone
Normal to increased muscle tone
Urinary incontinence (upper motor neuron)
Spinal cord C1-C5
Abnormalities of gait in thoracic and pelvic limbs—ipsilateral Decreased or absent conscious proprioception Ataxia
Paresis (weakness)
Paralysis
Abnormal spinal reflexes—ipsilateral Hyperreflexia in both thoracic and pelvic limbs Decreased to absent caudal cervical and auricular reflexes Decreased to absent slap test (horses)
Altered muscle tone
Normal to increased muscle tone
Urinary incontinence (upper motor neuron)
Spinal cord C6-T2
Abnormalities of gait in thoracic and pelvic limbs—ipsilateral Decreased or absent conscious proprioception Ataxia
Paresis (weakness)
Paralysis
Abnormal spinal reflexes—ipsilateral Hyporeflexia in thoracic limbs Hyperreflexia in pelvic limbs Decreased to absent caudal cervical and auricular reflexes Decreased to absent slap test (thoracolaryngeal reflex, horses)
Absent panniculus reflex
Horner's syndrome (ipsilateral)
Altered muscle tone
Decreased muscle tone in thoracic limbs
Normal to increased muscle tone in pelvic limbs
Urinary incontinence (upper motor neuron)
Spinal cord T3-L2
Abnormalities of gait in pelvic limbs only—ipsilateral Decreased or absent conscious proprioception Ataxia
Paresis (weakness)
Paralysis
Abnormal spinal reflexes—ipsilateral Hyperreflexia in pelvic limbs only Decreased panniculus reflex caudal to lesion
Altered muscle tone—ipsilateral
Normal to increased muscle tone in pelvic limbs Urinary incontinence (upper motor neuron)
Spinal cord L3-S3
Abnormalities of gait in pelvic limbs only—ipsilateral Decreased or absent conscious proprioception Ataxia
Paresis (weakness)
Paralysis
Abnormal spinal reflexes—ipsilateral
Hyporeflexia in pelvic limbs only
Altered muscle tone
Decreased muscle tone in pelvic limbs
Flaccidity of the tail
Urinary incontinence (lower motor neuron) Fecal incontinence (lower motor neuron) Peripheral nerve and muscle
Abnormalities of gait
Paresis to paralysis
Decreased or absent conscious proprioception
Ataxia
Paresis (weakness)
Paralysis
Abnormal spinal reflexes—ipsilateral
Hyporeflexia
Altered muscle tone
Decreased muscle tone
Muscle atrophy Flaccidity of the tail
Urinary incontinence (lower motor neuron)
Fecal incontinence (lower motor neuron)
The clinical signs of neurologic disease depend on the location of the disease process within the nervous system (Table 8.1). Widely varying disease entities may produce similar or identical clinical signs.
Seizures, for example, may be the result of metabolic, toxic, traumatic, neoplastic, or other causes. Definitive diagnosis of neurologic disease, therefore, cannot be made based on clinical signs alone. Localization of lesions within the nervous system by meticulous physical and neurologic examination is the first and key step in developing a differential diagnosis list and a rational diagnostic and therapeutic plan.