Combined Upper and Lower Motor Neuron Syndromes

MOTOR NEURON SYNDROMES

Motor neuron disease refers to a group of disorders in which selective degeneration of both upper and lower motor neurons occurs. y Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease) is the prototypical motor neuron disease. Several varieties or subtypes are recognized based on the sites at which the motor neurons are first and most prominently involved. The spinal form most commonly

TABLE 15-12 -- EXAMPLES OF COMMON NEUROPATHIES CAUSING WEAKNESS

Neuropathy

Patterns of Muscle Weakness and Reflex Changes

Common Causes

Long thoracic nerve (C5-C7)

Winged scapula (serratus anterior)

Pressure on shoulder, weight lifting

Axillary nerve (C5-C6)

Abduction of arm (deltoid)

Dislocated shoulder, brachial neuritis

Musculocutaneous nerve (C5-C7)

Flexion of forearm (biceps), biceps jerk

Infarction due to vasculopathy (DM, PAN)

Median nerve (C5-T1)

Abduction (abductor pollicis brevis, opponens pollicis) and opposition of thumb

Entrapment--pronator or carpal tunnel syndrome

Ulnar nerve (C7-T1)

Intrinsic muscles of hand except those innervated by median nerve; "claw hand"

Pressure at elbow, entrapment in cubital tunnel

Radial nerve (C5-C8)

Extensors of wrist and fingers, "wrist drop" triceps, triceps jerk (if compressed in axilla)

Pressure in axilla ("crutch palsy") or spiral groove of humerus ("Saturday night palsy")

Femoral nerve (L2-L4-)

Flexion of thigh, leg extension (psoas, quadriceps), knee jerk

Surgical trauma, DM

Common peroneal nerve (L4 1.5)

Dorsiflexors and everters of foot

Pressure palsy at fibular head

DM, Diabetes mellitus; PAN, polyarteritis nodosa.

DM, Diabetes mellitus; PAN, polyarteritis nodosa.

affects the lumbosacral segments first, producing weakness, atrophy, and fasciculations in one leg as the initial manifestations. At the same time, the upper motor neurons are generally affected, so instead of loss of reflexes to accompany the atrophy and fasciculations, hyperreflexia occurs, producing the characteristic combination of upper and lower motor neuron involvement. Onset of disease in the brain stem affects the lower cranial nerve nuclei, producing a progressive bulbar palsy. Lower motor neuron degeneration becomes evident by weakness, atrophy, and fasciculations of the tongue and weakness of voluntary palatal movement, while upper motor neuron involvement is shown by the very brisk gag reflex and jaw jerk. The otolaryngologist is often the first consultant asked to see the patient because a nasal voice and dysphagia are present. Occasionally, the upper motor neurons are selectively affected at the onset, producing a slowly progressive spastic tetraparesis and pseudobulbar palsy (primary lateral sclerosis). Often an EMG can record the fibrillations, positive sharp waves, and giant action potentials typical of lower motor neuron involvement before the signs become clinically manifest. Regardless of the mode of onset, the disorder eventually involves the motor neurons of the entire neuraxis.

From a diagnostic standpoint, it is most important to differentiate ALS from potentially treatable lesions in the cervical canal that compress the nerve roots and spinal cord, producing a characteristic syndrome of lower motor neuron signs in the hands and upper motor neuron signs in the legs. Imaging of the cervical spine is important to rule out cervical spondylosis or tumor. ALS is confirmed by electromyographic demonstration of denervation in a combination of facial or bulbar muscles and lower extremities.

Paralytic poliomyelitis is now rare in the vaccinated western world. The neurotrophic polio virus attacks nerve cells in the hypothalamus, thalamus, brain stem, reticular formation, vestibular nuclei, and nuclei of the cerebellum, but the major hallmark of the disease is destruction of the lower motor neurons in the motor nuclei of the brain stem and anterior horn of the spinal cord. The severity and distribution of the bulbar and spinal paralysis is quite variable. The most common bulbar symptoms are weakness of the face, larynx, and pharynx. Spinal paralysis is more common than bulbar paralysis. Weakness develops rapidly, usually attaining its maximum severity in 48 hours, and is accompanied by coarse fasciculations. The tendon jerks may be hyperactive during the acute phase but then diminish and eventually are lost as the weakness of the limb muscles progresses. Limb weakness is often asymmetrical and patchy. Muscle atrophy is generally appreciated within 3 to 4 weeks of the paralysis and is permanent. In addition to the disability produced by the weakness and atrophy, progression of muscle weakness may occur many years after the acute paralytic illness (postpolio syndrome).

MYELOPATHIC SYNDROMES

The transverse myelopathy syndrome interrupts the ascending tracts from below the level of the lesion and all descending tracts from above this level. Therefore, all motor and sensory function below the level of the spinal cord injury is lost. Trauma is the most frequent cause of complete loss of function at the site of the injury. In practice, many lesions are incomplete, although there is evidence of involvement of the entire cross-sectional extent of the cord. Demyelinating and inflammatory processes account for most examples of incomplete lesions and are often referred to as transverse myelitis. All sensory modalities are lost below the level of the lesion. There is often a zone of disagreeable dysesthesia at the uppermost border of the sensory loss. Radicular pain is common at the level of the lesion. If an infectious or neoplastic process is present in the epidural space (epidural abscess) or in the vertebrae (metastatic cancer), localized vertebral pain may be elicited by percussion of the spinous processes.

The pathological processes that produce transverse myelopathy are often acute and initially produce a flaccid areflexic paralysis known as spinal shock ( .Table 15-13

). Within days, the motor syndrome becomes characteristic of an upper motor neuron paralysis with hyperreflexia and bilateral extensor plantar responses. At the level of the lesion, segmental lower motor neuron signs may persist owing to injury to the anterior horns or the ventral roots. The lower motor neuron signs are a reliable indicator of the level of the spinal cord injury. They may be quite obvious in the cervical level but can be subtle and hard to detect at the thoracic cord level.

Marked disturbances in autonomic function can occur below the level of the lesion. Loss of sweating and trophic skin changes occur, as well as loss of temperature control and vasomotor instability, which can result in sudden changes in body temperature and blood pressure, including hypertensive crises. Initially, after an acute lesion, the bladder

TABLE 15-13 -- MYELOPATHIES OR SPINAL CORD SYNDROMES

Location of Lesion

Characteristic Signs

Complete transection

Complete loss of motor and sensory function below level of lesion (tetraplegia or paraplegia)

(transverse)

Acute: flaccid, areflexia (spinal shock)

Chronic: spasticity, hyperreflexia, Babinski's signs, spastic bladder

Hemisection (Brown-Sequard

Ipsilateral hemiplegia or monoplegia, ipsilateral loss of vibration, proprioception

syndrome)

Contralateral loss of pain and temperature below level of lesion

Central

"Suspended" sensory loss: "cape" sensory loss over shoulders from cervical lesion most common

Loss of pain and temperature, sparing of vibration and proprioception ("dissociated" sensory loss)

Weakness, atrophy, fasciculations, loss of reflex in extremity of affected segment (usually arm or cervical)

Anterior (anterior spinal artery

Loss of motor function below level of lesion, flaccid tetraplegia or paraplegia. Loss of pain and temperature sensation below level of

syndrome)

lesion with preservation of vibration, proprioception. Loss of bladder and bowel control

Caudal (conus medullaris)

Hypotonic bladder and rectal sphincters. Pain and loss of sensation in saddle distribution in perineum

is atonic, and the anal sphincter is flaccid. Later they become spastic, leading to involuntary evacuation of the bladder and bowels.

The Brown-Sequard syndrome produces a characteristic combination of motor and sensory signs below the level of the lesion. Interruption of the descending corticospinal tract produces an ipsilateral spastic weakness. Also, ipsilateral loss of proprioception below the level of the lesion results from interruption of the ascending fibers in the posterior columns. Loss of pain and temperature sensation occurs contralateral to the hemisection because the crossed spinothalamic tract is interrupted. The sensory level that is responsive to pain and temperature is usually located one or two segments below the level of the lesion. When the Brown-Sequard syndrome results from an extramedullary lesion, there may be segmental lower motor neuron and sensory signs at the level of the lesion due to damage to the roots and anterior horn cells, and these signs are the most reliable indication of the level of the lesion. This syndrome is most apparent in patients with traumatic hemisections of the spinal cord (e.g., due to a stab wound). Other causes are extramedullary tumors or abscesses and, less commonly, intrinsic lesions, especially vasculitis (as in systemic lupus erythematosus). The full-blown hemisection syndrome is not commonly encountered (see T§ble...l§:13 ).

The central cord syndrome is most often caused by syringomyelia and intramedullary cord tumors. The pathological process starts centrally and proceeds centrifugally, producing motor and sensory signs that evolve characteristically for this syndrome. Characteristically, the syndrome presents as a combination of segmental loss of pain and temperature sensation and lower motor neuron signs. This patterns occurs because the crossing fibers of the spinothalamic tract conveying pain and temperature sensation are initially compromised but posterior column sensation is preserved ( disassociated sensory loss). Because only the decussating spinothalamic tract fibers are affected, the loss of pain and temperature is bilateral but affects only those segments of the spinal cord involved in the pathological cavitation or by the tumor, thus producing a suspended sensory loss with normal sensation above and below the lesion. In patients with syringomyelia, this pattern characteristically begins in the upper cervical segments, producing a loss of pain and temperature over the shoulders in a cape distribution. The syringomyelia or tumor usually invades the anterior horns early, producing the segmental lower motor neuron syndrome with weakness, wasting, and loss of reflex. As the lesion expands centrifugally, it may compromise the lateral corticospinal tracts, producing an upper motor neuron syndrome below the level of the lesion and loss of proprioception and vibratory sensation below the level of the lesion as it extends into the posterior columns (see Table 15-13 ).

When the anterior horns are affected in the cervical cord, wasting occurs first in one hand and then in the other. At the thoracic level the disease affects the lower motor neurons innervating the paraspinal musculature, resulting in a scoliosis. Finally, if the lesion extends into the spinothalamic tracts themselves, pain and temperature sensation below the level of the lesion may be lost. Because the spinothalamic tracts are arranged in a laminated pattern with the sacral segments in the most lateral and ventral position, the sacral dermatomes are often preserved (sacral sparing).

The anterior spinal artery syndrome produces a distinctive combination of motor and sensory signs. Circulation to approximately the ventral two-thirds of the spinal cord is supplied by the anterior spinal artery. Occlusion of the anterior spinal artery thus produces infarction in the ventral and most of the lateral funiculi, which include the anterior horns and the lateral corticospinal and spinothalamic tracts. Infarction leads to a subacute onset of a flaccid paralysis below the level of the lesion with loss of pain and temperature sensation below the level of the lesion. Position sense, vibration, and light touch are spared because the dorsal column supplied by the posterior spinal arteries is preserved. Infarction of the spinal cord usually occurs at border zones between the major arterial systems supplying the spinal cord. These watersheds are at the T1-T4 and L1 spinal cord levels.

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Responses

  • Mantissa
    What are upper and lower motor neurons?
    2 years ago
  • Rahel
    Is pot disease a lower motor neuron lesion?
    2 years ago
  • rita
    Which disease cause mixed of upper and lower motor lesions?
    12 months ago
  • Quintilia
    Which disease have both upper & lower motor neuron lesion mabifestation?
    11 months ago
  • layla
    Why conus medullaris have both UMN and LMN lesion?
    11 months ago
  • sven
    Can pain intercept the motor neuron?
    10 months ago
  • donna
    Is posterior cord syndrome upper or lower motor neuron?
    7 months ago
  • SAGRAMOR
    What conditions are both upper and lower motor neuron disorders?
    6 months ago
  • milen
    What diseases cause lower motor neuron lesion?
    6 months ago
  • Oronzo
    What conditions can cause upper motor neuron and lower motor neuron signs?
    3 months ago
  • BINGO
    Does polio affect upper motor neurons or lower motor neurons?
    3 months ago
  • Abaalom
    What is a disease that have both upper and lower motor neuron lesion character?
    1 month ago

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