History
A thorough history and physical examination are required to confirm the presence of neuropathic pain syndrome and are also important steps in reaching an etiologic diagnosis for neuropathic pain. Rapid and correct diagnosis of neuropathic pain should be done so that appropriate management can be started earlier. History will help determine whether the character and distribution of pain follow the neuropathic criteria and whether a relevant lesion or disease in the nervous system is probably responsible for the pain.
Pain Intensity
Pain intensity can be rated using a valid verbal, numerical, or visual analog scale or Numeric Pain Rating Scale, such as the Neuropathic Pain Scale and Neuropathic Pain Questionnaire, at each visit to monitor therapeutic response.
Description of Sensory Symptoms
The PQRST pain assessment is a systematic method used to evaluate a patient’s pain by assessing Provocation, Quality, Region (or Radiation), Severity (or Scale), and Timing. Pain may present as spontaneous sensations such as paresthesias (eg tingling, itching, sensation of something crawling on one’s skin, discomfort of one’s foot “falling asleep”), dysesthesias (eg pricking, electric shock-like, burning, or shooting pain), and phantom pain. The pain may also be stimulus-evoked pain or sensation, including conditions such as allodynia, hyperalgesia, hyperpathia, and hypoesthesia or anesthesia.
The quality of pain may be described in several ways, including burning, sharp, stabbing, cold, allodynia, hyperalgesia, spontaneous, dysesthesia, and paresthesia. Patients may also report frequent non-painful sensations, such as pricking, tingling, aching, numbness, hypoesthesia, anesthesia, hypoalgesia, and analgesia. Sensory abnormalities and pain may paradoxically coexist.
Temporal Variation of Pain
The pain usually becomes worse toward the end of the day. Rule out a neoplastic process if pain progressively increases over the recent months.
Functional Impact
Impact on behavior, mood, suicidal ideas, activities of daily living, instrumental activities of daily living, work, and socialization should be noted.
Review of Systems
Determine the involvement or affectation of other bodily systems.
Past Medical History
Other health conditions (both medical and surgical), current medications, and previous treatment usually resistant to medications (eg Paracetamol, nonsteroidal anti-inflammatory drugs [NSAIDs]) should be asked. Adequate titrated doses of specific drugs should be determined and documented. Personal and psychosocial history should also be noted.
Alcohol and Substance Abuse
A history of dependence disorders can affect decisions about prescribing opioids and cannabinoids. Consider the interaction of sedatives and alcohol with other substances.
Other Factors
Other factors to take note of include life stressors, family and social support, and resources.
Physical Examination
Neuropathic Pain_Initial AssesmentPhysical examination allows integration of the patient’s current symptoms and localization of the involved elements of the nervous system. Identifying pain localization, quality, intensity, and patterns is essential. These would reveal the presence of negative (loss of function) and positive (hyperalgesia and/or allodynia) signs for sensory modalities affecting the somatosensory system and relevance to the underlying disease or lesion.
Axial and Appendicular Examination
Changes in skin temperature, color, sweating, or hair growth (complex regional pain syndrome) should be noted. Residual dermatomal scars may persist after herpes zoster infection. Look for characteristic skin changes of diabetes mellitus.
Motor Examination
Motor examination may reveal motor weakness depending on the lesion in the nervous system or health condition. This involves checking the range of motion, muscle tone (normal, hypotonic, or hypertonic), and strength (Manual Muscle Testing). Patterns include muscle groups in case of central involvement, myotomes in case of spinal cord or spinal nerves, and representative muscles for the involved and non-involved peripheral nerves.
Muscle Stretch Reflex or Deep Tendon Reflex
Muscle stretch reflex, or deep tendon reflex, may be decreased or absent in the distribution of the affected nerve. A hyperreflexic finding is suggestive of central nervous system involvement, while an absent or hyporeflexic result is suggestive of peripheral nervous system.
Sensibility Examination
Sensibility examination includes reduced or absent light touch, pinprick, vibration responses, and proprioception in the affected nerve territory. Sensory disturbances can expand outside the area of nerve innervation. Dynamic allodynia is the pain arising from gentle brushing of skin with a cotton ball. Thermal allodynia is a burning sensation due to an ice cube placed on the skin. Hyperalgesia to pinprick test. Pain on leg lifting may mean irritation of lumbar nerve roots. Myofascial trigger points show myofascial pain plus neuropathic pain.
Other Tests for Consideration
Other tests include Lhermitte’s sign, for possible cervical spine irritation; Spurling’s test, for cervical radiculopathy; Phalen’s test, for carpal tunnel syndrome; Tinel sign, for carpal tunnel or cubital tunnel syndrome; the femoral nerve stretch test, for L2-L4 radiculopathy; and the slump test or straight leg raising, for sciatic nerve injury/tension.
Screening
The main advantage of screening is to identify potential patients with neuropathic pain, particularly by non-specialists.
Screening Tools
Screening tools include Unidimensional scales, McGill pain questionnaire, Douleur Neuropathique en 4 Questions (DN4) questionnaire, ID-Pain questionnaire, PainDETECT questionnaire, Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) pain scale, Standardized Evaluation of Pain (StEP), Chinese Identification Pain questionnaire, and Self-administered version of LANSS (self-administered LANSS [S-LANSS]) and DN4 (self-administered DN4 [I-DN4]).
Assessment Questionnaires
Assessment questionnaires include the Brief Pain Inventory (BPI), Neuropathic Pain Scale (NPS), and Neuropathic Pain Symptom Inventory (NPSI).
Clinical Neurophysiology and Electrodiagnostic Test
Clinical neurophysiology and electrodiagnostic tests are psychophysiological measures of perception in response to external stimuli of controlled intensity, which allow documentation of sensory profiles. This is appropriate to quantify positive sensory phenomena like mechanical and thermal allodynia and hyperalgesia, which may help characterize painful neuropathic syndromes and predict or monitor treatment effects.
Neurophysiological Testing
Neurophysiological testing is a standard neurophysiological response to an electrical stimulus that can identify, localize, and quantify damage along peripheral or central sensory pathways. For pain-related evoked potential, laser-evoked potentials are the easiest and most reliable methods for assessing the function of the nociceptive and A-delta fiber pathways in patients with neuropathic pain. Electromyography (EMG) and nerve conduction velocity (NCV) provide objective evidence of nerve injury or dysfunction but primarily evaluate the large myelinated fibers; thus, small fiber neuropathy may not be ruled out if the result is normal. Microneurography provides valuable information on the physiology and pathophysiology of all nerve fiber groups but this is not recommended as routine procedure for assessing patients with peripheral neuropathic pain. Pain-related reflexes are diagnostically useful only for facial pains, as in trigeminal pain disorders.