Sensory Examination

Michael Ronthal

▪ INTRODUCTION

The symptoms of sensory dysfunction vary according to the sensory pathway involved. A good approach is to separate out the main functional pathways. In the peripheral nerve, large fiber (mainly proprioceptive) versus small fiber (mainly nociceptive) function can be distinguished. Centrally, in the spinal cord the functional division is posterior column system versus the ascending spinothalamic tract. Above the level of the thalamus the distinction is not clearly demarcated, but the posterior part of the insular cortex plays a large role in nociceptive sensation.

Broadly speaking, the subjective sensory complaint points to the pathway, but not always to the site of pathology.

Dysfunction in the proprioceptive pathways leads to the subjective complaint of deep aching, gnawing pain; tight, squeezing garter sensations in the limbs; or nondescript, sometimes bizarre paresthesias. For example, patients may report that their fingers feel swollen or ballooned.

The subjective sensation of nociceptive dysfunction is primarily superficial pain that may be sharp and localized, spontaneous, or reactive, or it may present as feelings of heat or coldness. Itching is a form of nociceptive pain.

▪ EXAMINATION

Nociceptive Pathway

A new pin is required for the examination of each patient. A proprietary Neurotip serves us well. This is a small plastic rod with a metal point at one end and a blunt plastic tip at the other, but a new safety pin and sharp broken orangewood stick work as well. The pin should be just sharp enough to elicit the sensation of mild pain but not sharp enough to pierce skin.

The patient must be educated to report subjective sensation. Simply pricking with a pin and asking “do you feel this?” is inadequate because a touch sensation will yield a “yes” response, when in fact pinprick sensation is deficient. Test a normal area first to establish the parameters.

In the face, the three divisions of the trigeminal nerve territory are tested—forehead, check, and chin (Fig. 3.1).

For the body, testing starts at the back of the head (C2). Work downward over the angle of the jaw (C3), shoulder (C4), and lateral upper limb (C5 and 6), and then ascend up the medial side of the upper limb to the axilla (T3). Over the anterior chest wall the approximate level of the nipple line demarcates cervical territory (C4) from thoracic territory (T4). Proceed caudally down the trunk, passing over the lower costal margin (T8) and umbilical level (T10) to the groin (T12/L1). Sensation should also be tested posteriorly and paraspinally (Fig. 3.2).

In the lower limb, testing starts in the upper medial thigh, downward over the medial leg, then the lateral leg, the dorsal aspect of the foot, and the lateral foot and then up the posterior midline of the lower limb to the buttock and perianal region. Loss of pinprick sensation over
the lateral thigh is never dermatomal because of crowding of dermatomes and almost always is part of a lateral cutaneous femoral nerve syndrome (meralgia).

Only gold members can continue reading. Log In or Register to continue