Numbness and tingling

Also known as: Paresthesias, dysesthesias, hypesthesias, sensory loss, loss of sensation

Anatomy or system affected: Legs, muscles, musculoskeletal system, nerves, nervous system, skin

Definition: Abnormalities of sensation that are attributable to nerve damage or disorders

SymptomsPatients commonly report various sensory aberrations that are often described as “pins and needles,” tingling, prickling, burning of varying severity, or sensations resembling electric shock. The accepted term for these symptoms is paresthesiasor dysesthesias. When severe enough to be painful, they can be referred to as painful paresthesias.

The other major sensory symptom is a reduction or loss of feeling in an area of skin. Most patients use the relatively unambiguous term numbness; however, the more formal medical term is hypesthesia. Paresthesias, dysesthesias, and hypesthesias are usually restricted to a part rather than all of the cutaneous territory of a damaged root or nerve.

The distribution of nonparesthetic pain is seldom as anatomically specific as the paresthesias themselves. Patients with carpal tunnel syndrome, for example, often have arm and shoulder pain that suggests compression of a cervical root rather than of the distal median nerve (a combined motor and sensory nerve). The paresthesias, by contrast, are usually localized to the tips of the fingers innervated by the median nerve. Similarly, in patients with cervical or lumbosacral radiculopathies (any diseased condition of the roots of spinal nerves), the distribution of pain in the upper or lower limbs often correlates poorly with the root involved. The paresthesias, however, are usually felt either along the entire area or, more commonly, in the distal part of the skin area innervated by the damaged root (the dermatome).

Examination. In attempting to localize the site of a lesion, the physician innervates major muscles from the spinal nerve roots (myotomes) through the plexuses, the individual peripheral nerves and their branches, and also the cutaneous areas supplied by each of these components of the peripheral nervous system. Traditionally, the site of the lesion can be deduced from which muscles and nerves are involved and from where the various branches of the peripheral nerves arise.

In motor examination, the muscles and tendon reflexes are examined first because weakness and reflex changes are often easier to elicit than sensory signs. The muscles are first examined for atrophy. Since muscles become atrophic when denervated, the focal atrophy can sometimes accurately identify a nerve lesion. The lack of atrophy in a weak muscle either indicates an upper motor neuron lesion or raises the suspicion of spurious weakness. A systematic examination of individual muscles is then performed.

In sensory examination, the patient describes the area of sensory abnormality, which often tells as much as a formal examination. Testing light touch with the examiner’s finger is frequently all that is required for confirmation. If this reveals no abnormality, retesting with a pin may disclose an area of sensory deficit. Pinpricks in normal and abnormal areas are compared.

It is important to examine the entire course of an affected nerve for bone, joint, or other abnormalities that may be causing the nerve damage. Local tenderness of the nerve and/or a positive Tinel’s sign (paresthesias produced in the area of the nerve when the nerve is tapped or palpated) may also help to identify the site. Many normal persons experience mild tingling when nerves such as the ulnar at the elbow or the median at the wrist are tapped lightly, so this finding is significant only when the nerve is very sensitive to light percussion. Conversely, a badly damaged nerve may be totally insensitive to percussion or palpation.

Nerve conduction studies and the electromyographic examination of muscles evaluate the function of large-diameter, rapidly conducting motor and sensory nerve fibers. These two complementary techniques are valuable tools in the accurate assessment of focal peripheral neuropathies, helping in the localization of the nerve lesion and the assessment of its severity.

Diagnosis. Peripheral nerves causing sensory symptoms may be damaged anywhere along their course, from the spinal cord to the muscles and skin that they innervate. The site of a focal neuropathy (the focus of neurologic disease) may therefore be in the nerve roots, the spinal nerves, the ventral or dorsal rami (branches), the plexuses (network of nerves), the major nerve trunks, or their individual branches. The character, site, mode of onset, spread, and temporal profile of sensory symptoms must be established, and precipitating or relieving factors identified. These features—and the presence of any associated symptoms—help identify the origin of sensory disturbances, as do the physical signs. Sensory symptoms or signs may conform to the territory of individual peripheral nerves or nerve roots. Involvement of one side of the body or of one limb in its entirety suggests a central lesion. Distal involvement of all four extremities suggests polyneuropathy (several neurologic disorders), a cervical cord or brain-stem lesion, or when symptoms are transient, a metabolic disturbance such as hyperventilation syndrome. Short-lived sensory complaints may be indicative of sensory seizures or cerebral ischemic phenomena (local and temporal deficiency of blood supply caused by obstruction of the circulation to a part), as well as metabolic disturbances. In patients with cord lesions, there may be a transverse sensory level. Dissociated sensory loss is characterized by the loss of some sensory modalities and the preservation of others. Such findings may be encountered in patients with either peripheral or central disease and must therefore be interpreted in the clinical context in which they are found.

The absence of sensory signs in patients with sensory symptoms does not mean that symptoms have a nonorganic basis. Symptoms are often troublesome before signs of sensory dysfunction have had time to develop.

It is vital to remember paresthesias is often a temporary condition caused by issues such as migraines, whiplash, anxiety, and dehydration. When the condition is not transient, it becomes chronic and more serious medical conditions need to be investigated.

Bibliography

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National Institute of Neurological Disorders and Stroke. "NINDS Paresthesia Information Page." National Institute of Neurological Disorders and Stroke, May 6, 2010.

“Paresthesia: What It Is, Causes, Symptoms & Treatment.” Cleveland Clinic, 26 Apr. 2023, my.clevelandclinic.org/health/symptoms/24932-paresthesia. Accessed 31 July 2023.

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