Diagnosing Nerve Pain

Nerve pain, also known as neuropathic pain, and centralized pain conditions are common but are often not diagnosed or are diagnosed late. The suffering is significant, and patients are frequently not taken seriously by their social environment, leading to a drastic reduction in quality of life. 

See also the section ‘Complaints – Nerve Pain’ for more details. Common nerve pain conditions include:

• Postherpetic neuralgia
• Trauma-induced nerve injury
• CRPS (Complex Regional Pain Syndrome)
• Chronic back pain
• Painful polyneuropathy due to metabolic disorders (e.g., diabetes mellitus)
• Post-chemotherapy
• Fibromyalgia / Widespread Pain

Neuropathic and centralized pain have typical clinical signs:

• Hyperalgesia: An ordinarily painful stimulus (e.g., a pinprick) is perceived as significantly more painful in the affected area compared to a non-affected area.
• Hypoesthesia: A stimulus such as light touch, temperature, or vibration is perceived less intensely.
• Allodynia: A normally non-painful stimulus (e.g., touch with a brush or cotton wool) is perceived as painful.
• Increased Pain Sensitivity: Chronic pain often results in increased sensitivity to pain.

The examination is performed at the site of maximum (sensory) symptoms and compared with a healthy, unaffected site.

 QST – Quantitative Sensory Testing

Nerve pain and centralized pain conditions are professionally diagnosed through “quantitative sensory testing” (QST). QST is a psychophysical method to quantify the functional status of the somatosensory system. It evaluates all types of afferent (sensory) nerve fibers by applying quantitative and graded stimuli (graded Vvon Frey hairs, multiple pinprick stimuli, pressure algometer, quantitative thermal testing, tuning fork, etc.) using specific test algorithms. Performing QST correctly requires experience and specialized equipment.

It is important to note that while QST can be useful, it is not necessarily required to diagnose a neuropathic pain condition. QST examinations are not conducted at the ISSZ but are referred to our partner institute IISZ in Zurich when indicated.

If clinical indications of a neuropathic pain condition exist and further investigation is necessary, QST can be a helpful diagnostic tool. It allows for differentiation between neuropathic and non-neuropathic pain conditions. When standard electrophysiological tests appear normal but a small fiber neuropathy is suspected, QST can reveal deficits in the function of sensory nerve fibers.

QST does not have standalone diagnostic value and should be used as an additional diagnostic tool. It must be interpreted in a broader context and in conjunction with the results of bedside clinical examinations, pain questionnaires, sensory nerve conduction studies (electroneurography), and somatosensory evoked potentials.