Peripheral Neuropathy

Peripheral Neuropathy: Excerpt from Field Guide to Bedside Diagnosis

Differential Overview

❑ Diabetes

❑ Alcohol

❑ Vitamin B₁₂ deficiency

❑ Drugs

❑ Carcinomatous

❑ Lead

❑ Guillain-Barré

❑ Tabes dorsalis

❑ Syringomyelia

❑ Polyarteritis nodosa

❑ Amyloidosis

❑ Polymyositis

❑ Pellagra

❑ Arsenic

❑ Porphyria

❑ Wallenberg syndrome

❑ Thalamic lesion

❑ Brown-Sequard syndrome

Diagnostic Approach

Sensory neuropathy symptoms include positive phenomena such as tingling; pins/needles; and burning, cold, or lancinating pain. Physical findings include weakness, fasciculations, atrophy, ataxia, wide-based gait, abnormal sweating, decreased or absent deep tendon reflexes, orthostatic hypotension, hypesthesia surrounded by a zone of hyperesthesia, and vibration or position sense affected before pinprick or temperature sense.

Autonomic neuropathy symptoms include impotence, retrograde ejaculation, diaphoresis, incontinence, urinary retention, constipation, diarrhea, orthostatic dizziness, and flushing. Physical findings include delayed pupillary light response, resting tachycardia, sinus arrhythmia, and orthostatic hypotension.

Sensory loss confined to part of a limb suggests injury to a peripheral nerve, plexus, or spinal root, resulting from trauma, entrapment, or vascular insufficiency. Mononeuropathy multiplex affects multiple nerves over time (e.g., due to diabetes or vasculitis). Polyneuropathy occurs in a stocking-glove distribution starting with the longest nerves, and is due to axonal neuropathy, with a toxic or metabolic origin. Bilaterally symmetrical symptoms are found in polyneuropathy or spinal cord lesions, while unilateral involvement is seen in contralateral disease of the brainstem, thalamus, or cortex.

Injury to large myelinated nerves produces decreased light touch and proprioception with a sensation of “walking on a thick carpet” or imbalance. Injury to medium fibers causes decreased light touch and vibration sense. Injury to small unmyelinated fibers, as occurs in diabetes or amyloidosis, decreases pain and temperature sensation and produces dysesthesias. Disproportionate loss of vibration sense and proprioception compared with pain and temperature sensation occurs with diseases of the dorsal column of the spinal cord (e.g., neurosyphilis, vitamin B ₁₂ deficiency, or multiple sclerosis) and demyelinating polyneuropathy.

Transverse cord lesions produce loss of all modalities below the level of the lesion and a band of hyperalgesia at the level of the lesion. Lateral cord compression is heralded by early sensory changes. Dorsal cord compression affects proprioception and tactile discrimination without pain or temperature loss. Pernicious anemia and tabes dorsalis preferentially affect the dorsal columns.

Clinical Findings

Diabetes  A symmetrical stocking-glove distribution is typical. Vibration and position sense is most prominently impaired initially, followed by decreased reflexes and periods of painful paresthesias and vasomotor disturbance.

Alcohol  A symmetrical stocking-glove neuropathy in an alcoholic patient may result from thiamine deficiency or the direct toxic effect of alcohol.

Vitamin B₁₂ deficiency  It presents with progressive paresthesias and dysesthesias of the lower extremities. Combined system disease (pyramidal, posterior column, and peripheral neuropathy) is present.

Drugs  Peripheral neuropathy is a common side effect of chemotherapeutic agents such as vincristine.

Carcinomatous  This neuropathy combines findings of a sensory polyneuropathy, muscle weakness and wasting—often with a myasthenic pattern—and
subacute combined degeneration with tremor, ataxia, and dysequilibrium.

Lead Abdominal pain, headache, ataxia, and memory loss are concurrent with the neuropathy.

Guillain-Barré  Paresthesias are rapidly followed by the development of areflexia, weakness, and paralysis. The symptoms begin distally in the hands and feet and ascend proximally. Sensory loss is minimal compared with weakness, and predominantly affects the larger myelinated fibers carrying proprioception and vibration.

Tabes dorsalis  Syphilis is suggested by paroxysmal onset, absent deep tendon reflexes, absent dorsal column function, and an Argyll Robertson pupil (accommodates but does not react to light).

Syringomyelia  It presents with a capelike (across the upper back, shoulders, and upper arms) loss of pinprick and temperature sensation while sparing other modalities.

Polyarteritis nodosa  Consider vasculitis when polyneuritis is associated with fever, weight loss, or arterial lesions.

Amyloidosis  It may present as a symmetrical or asymmetrical sensory–motor neuropathy. The key to diagnosis is recognition of concomitant macroglossia, waxy purpuric periorbital lesions, hepatomegaly, or congestive heart failure.

Polymyositis  It presents as pain in the extremity with proximal weakness, loss of reflexes, and decrease in position and vibration sense.

Pellagra  It presents not only with subacute combined degeneration, but also with a symmetrical photodermatitis, which is brownish with a curious varnished surface appearance.

Arsenic  Burning paresthesias in a glove or stocking distribution combined with palmar hyperkeratosis suggests arsenic intoxication.

Porphyria  Neuropathic pain, which is associated with acute weakness, and abdominal pain (colic) are prominent features. The urine will turn a burgundy color if left exposed to light.

Wallenberg syndrome  A lesion of the lateral medulla involves pain and temperature loss on the ipsilateral face and contralateral limbs and trunk. An ipsilateral Horner syndrome, vertigo, nystagmus, hoarseness, and dysphagia are also present.

Thalamic lesion  A contralateral sensory deficit involves all modalities, causing paresthesias, hyperesthesias, and hyperpathia (unpleasant burning pain with stimulation). It is most commonly due to a hypertensive lacunar infarct.

Brown-Sequard syndrome  Characterized by reduced proprioception, vibration, and weakness on the side ipsilateral to the lesion, and decreased
pinprick and temperature sensation on the contralateral side.

Pictures

Book Source Details

• Book Title: Field Guide to Bedside Diagnosis
• Author(s): David S. Smith
• Year of Publication: 2007
• Copyright Details: Field Guide to Bedside Diagnosis, Copyright © 2007 Lippincott Williams & Wilkins.

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More About This Book: Title: Field Guide to Bedside Diagnosis Authors: David S. Smith Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 0-78178-165-5

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