Evaluation of paresthesias

Paresthesias are abnormal sensory symptoms typically characterized as tingling, prickling, pins and needles, or burning sensations. They may be transient or persistent, limited in distribution or generalized, and may involve any portion of the body innervated by sensory or afferent nerve fibers. They may occur in isolation or in association with reduced or absent sensation. The symptoms usually occur spontaneously. Paresthesias can be caused by a dysfunction or abnormality affecting any level of the somatosensory pathway. However, the most common causes affect peripheral sensory nerves.

The somatosensory pathway

Primary afferent or sensory nerve fibers originate as unmyelinated nerve endings in the epidermis or as myelinated nerve fibers associated with sensory receptor structures in the dermis. They are organized distally as cutaneous branches of peripheral nerves or as the sensory components of mixed sensory and motor peripheral nerves, such as the median nerve in the hand or the tibial nerve in the leg. In the extremities, the peripheral sensory nerves become components of either the brachial plexus for the upper extremities or the lumbosacral plexus for the lower limbs. Proximal to the plexus, sensory nerve fibers remain combined with the motor nerve fibers in the spinal nerve roots, with the sensory nerve fibers projecting centrally to the dorsal root ganglion. The dorsal root ganglia contain the sensory neuronal cell bodies and are found alongside the spinal cord for the neurons innervating the extremities and trunk, or in the cranial nerve nuclei in the brainstem for the cranial nerves. The central process of the dorsal root ganglion neuron extends centrally, via the dorsal root, into the dorsal horn of the spinal cord, or from the cranial nerve sensory nuclei, with central projections through the thalamus and ultimately to the somatosensory cortex.[Figure caption and citation for the preceding image starts]: Ascending sensory pathways of the spinal cord. The dorsal column system and spinothalamic tract are the major ascending pathways that connect the periphery with the brain.Betts JG, Young KA, Wise JA et al.Anatomy and physiology. Houston, TX:OpenStax; 2013 (CC BY4.0 - https://creativecommons.org/licenses/by/4.0/) [Citation ends].