Lidocaine test in neuralgia.

Area of Science:

• Neurology
• Pain Medicine
• Clinical Pharmacology

Background:

• Chronic neuropathic pain following nerve injury presents complex sensory disturbances.
• Accurate diagnosis of these disorders is challenging, requiring effective assessment tools.

Purpose of the Study:

• To evaluate the effects of intravenous lidocaine on psychophysical somatosensory variables in patients with neuropathic pain.
• To assess the potential of intravenous lidocaine as a diagnostic aid for nerve injury-related sensory disorders.

Main Methods:

• Ten patients with nerve injury-induced chronic neuropathic pain were administered intravenous lidocaine or saline.
• Psychophysical somatosensory variables including pain magnitude, mechanical hyperalgesia, and thermal hyperalgesia were assessed.
• Conventional somatosensory testing with area mapping and subjective magnitude estimation were employed.

Main Results:

• Intravenous lidocaine transiently improved spontaneous pain and mechanical hyperalgesia in all 10 patients.
• Areas of hyperalgesia extending beyond the nerve territory also showed transient improvement with lidocaine.
• Saline injection resulted in transient improvement in only one patient, likely due to a placebo effect.

Conclusions:

• Intravenous lidocaine demonstrates efficacy in transiently alleviating spontaneous pain and mechanical hyperalgesia in neuropathic pain.
• Lidocaine's ability to inhibit anomalous neural impulses supports its proposed role as a diagnostic aid.
• This transient pain relief can facilitate a more comprehensive identification of sensory loss areas in patients with nerve injury.