Chapter 13 - Evaluation of the patient with "numbness"

Questions

Define the following terms:

conscious proprioception, agnosia (sterioagnosia), graphesthesia, dermatome, sclerotome, myotome, radiculopathy, myelopathy, anesthesia/hypoesthesia, hyperpathia, allodynia, hyperesthesia, dysesthesia, paresthesia, polyneuropathy, subjective.
Conscious proprioception is the ability to tell where a body part is in space. It is largely based on joint position sense.
Agnosia (sterioagnosia) is the inability to recognize what a sensation is despite relatively normal perception of the sensation. When it is tactile it is termed sterioagnosia (or asteriognosis). It would be the inability to determine the denomination of a coin despite normal ability to perceive it, for example.
Graphesthesia is the ability to identify letters or figures traced on the skin (without looking).
Dermatome is the area of skin supplied by a nerve root.
Sclerotome is the area of bone and joints supplied by a single nerve root.
Myotome is the muscles supplied by a single nerve root.
Radiculopathy is damage to a nerve root (radiculitis is irritation).
Myelopathy is damage to the spinal cord from any cause.
Anesthesia/hypoesthesia is loss (or decrease) in sensation.
Hyperpathia is the exaggerated perception of normally painful stimuli.
Allodynia is the perception of normally innocuous stimuli as being painful.
Hyperesthesia is excessive sensitivity to any modality.
Dysesthesia is the perception of the pain when no stimulus is present.
Paresthesia is the abnormal perception of a sensation in the absence of any stimulus.
Polyneuropathy is generalized damage to peripheral nerves. This is usually due to a systemic cause.
The sensory exam is by definition subjective, that is, relies on the patient's report.

13-1. What is the first step in evaluating the patient with “numbness”?

13-1. You must determine what the patient is referring to as numbness. Is it paresthesia, or a decrease in sensitivity that they are describing? Most cases of tingling do not result from central nervous system damage (other than a migraine or seizure). Most tingling results from peripheral nervous system problems.

13-2. What is important about the distribution of the symptoms?

13-2. The distribution of numbness is very important since this is key to localizing the lesion. Lost sensitivity is confined to within the distribution of the neural structure responsible. If the symptoms are intermittent, you must assess the reliability of the patient in localizing the symptom that they had.

13-3. What conclusions can you draw regarding patient having large areas of diminished sensitivity?

13-3. Loss of sensitivity covering large areas of the body (especially on one side, and especially involving the face and hand) is the best suggestion of central nervous system involvement.

13-4. What is the role of identifying precipitants for the symptoms?

13-4. This is the best indicator of cause.

13-5. What is Tinel sign and why is it important?

13-5. This is the generation of paresthesias in the distribution of a nerve following a light tap with a reflex hammer. This suggests an excessive excitability of nerve due to some focal damage. It is quite sensitive, but not very specific for conditions such as entrapment neuropathy. It is very useful for localizing a lesion.

13-6. What is suggested by the presence of a "march" of sensory symptoms (paresthesias that progress from one area of the body to adjacent regions over time measured in minutes)?

13-6. This most commonly indicates migraine or a sensory seizure. This does not occur with cerebrovascular disease and is strong evidence against stroke or TIA.

13-7. What kind of sensory symptoms are common in panic, high anxiety states and hyperventilation?

13-7. Perioral and finger tingling are common in these states. This is particular true if the patient was distraught or under high stress levels at the time.

13-8. What reflex is helpful to test ophthalmic sensation?

13-8. Loss of sensations on the upper face can usually be quantified by corneal reflex (or by electrically testing blink reflex).

13-9. What is the common sensory loss from damage to the spinal cord?

13-9. Spinal cord lesions often result in sensory level (loss of sensations below lesion) due to damage to ascending sensory tracts. .This loss (especially of pin sensation) usually begins at least several segments below the level of the lesion of the tract.

13-10. What infectious process is a common cause of localized paresthesia in the elderly?

13-10. Recent tingling in an older patient should raise the suspicion of early zoster.

13-11. What characteristics suggest the presence of hysterical sensory loss?

13-11. Numbness of the face is a common hysterical presentation. This often follows artificial boundaries (such as the jaw line or the hair line). Additionally, patients often report significant differences in vibratory sense across the midline of bones that span the midline (such as the skull, sternum or pelvis).

13-12. What is the pattern of sensory loss seen in diffuse damage to peripheral nerves (polyneuropathy)?

13-12. Diffuse peripheral nerve injury (polyneuropathy) results in stocking (and, later, glove) sensory loss.

13-13. What distribution of sensory deficit would you expect in demyelinating disease?

13-13. Demyelination can produce virtually any pattern of sensory change. However, the region of sensory loss is not likely to be highly localized because tract damage in the CNS usually produces large regions of sensory change.

13-14. What distribution of sensory deficit would you expect in entrapment neuropathy?

13-14. In entrapment neuropathy, the region of sensory decrease should be confined to the distribution of the nerve. Usually, the further the nerve damage is toward the periphery, the sharper the boundary between normal and abnormal sensation. Any tingling in one upper limb should be intensively investigated for peripheral entrapment or thoracic outlet syndrome. It is noteworthy that pain from peripheral entrapment may be experienced well beyond the distribution of the nerve.

13-15. What is the likely implication of the patient with sensory decrease (esp. pain and temperature) on one side of the face and the other side of the body?

13-15. This pattern results from injury to the brain stem (particularly the lateral brain stem, due to damage to the spinothalamic tract and to the spinal tract of the trigeminal nerve).

13-16. What is the likely implication of the patient with sensory loss on the same side of the face and body?

13-16. This pattern results from a lesion rostral to the midbrain (such as the thalamus or sensory cortex).

13-17. What is the significance of a “suspended sensory loss” (loss of a modality, usually pain and temperature sense, on both sides of the upper body with preservation below)?

13-17. This pattern is highly suggestive of an intramedullary spinal cord lesion.

13-18. What is the most sensitive confirmatory laboratory test for entrapment neuropathy?

13-18. Nerve conduction studies are quite sensitive and objective in testing for suspected peripheral neuropathy or peripheral entrapment neuropathy.

13-19. What laboratory test for can test central conduction along sensory pathways?

13-19. Somatosensory evoked potentials test large diameter fibers and dorsal column-medial lemniscus function.

13-20. Your patient with chronic pain compains of paresthesias in a large area of a painful limb. How can you determine whether this is simply related to their pain?

13-20. If this is simply a pain-related phenomenon, the motor and reflex exam should be normal. Also, you should be able to reproduce (or exacerbate) the patient's paresthesia by pressure over painful sites that are not directly over nerve trunks.