The Effectiveness of Ultra-Sound Guided Erector Spinae Block With Betamethasone for Management of Truncal Chronic Post Herpetic Neuralgia.

Postherpetic neuralgia (PHN) is a syndrome described as zoster-associated pain persisting for more than 3 months after resolution of an initial herpes zoster (HZ) rash ("shingles").[This condition is considered to be the most prevalent and challenging complication associated with HZ infection. According to reports, around 75% of senior patients who contract HZ are likely to experience it. The incidence of it was observed to be 38.1%, 27.0%, and 19.0% at 1 month, 3 months, and 6 months, respectively, following the onset of zoster. Half of the patients who are more than 50 years have the risk of developing PHN. It is noteworthy that the incidence of PHN seems to be on the rise.

Erector spinae plane (ESP) block is one of the newer interfascial techniques where the drug is injected below the erector spinae muscle to spread towards the costotransverse foramina and origin of dorsal and ventral rami where it is supposed to work at the origin of spinal nerves, based on cadaveric and contrast studies. Cadaveric studies have also showed that a block at T5 level is sufficient to have unilateral multi-dermatomal sensory block ranging from T1 to L3. Thus, this block serves the purpose of a paravertebral block without the risk of pleural injury.

Betamethasone is a long-acting corticosteroid with immunosuppressive and anti-inflammatory properties. It can be used topically to manage inflammatory skin conditions such as eczema, and parenterally to manage several disease states including autoimmune disorders. Betamethasone has potent glucocorticoid activity and negligible mineralocorticoid activity. The beneficial effects of injecting steroids could be because of sympathetic blockage, thereby inhibiting vasoconstriction and due to anaesthetization of the dorsal root ganglion and posterior spinal nerve.

Inclusion criteria

• Patients age between 18 and 75.
• Patients with American Society of Anesthesiologists (ASA) II and III status.
• Patients diagnosed with truncal chronic post herpetic neuralgia( neuropathic pain persistent for more than 3 months from the onset of rash appearance )

Exclusion criteria

• Patients unable to comprehend the informed consent.
• Patients on long term opioid regimens.
• Patients with impairment in hepatic (Alanine aminotransferase (ALT) >50 U/L, and/or Aspartate aminotransferase (AST): >45 U/L) or renal functions( creatinine level ≥1.5 mg/dL)
• Patients on anti-coagulation regimens.
• Patients with coagulation abnormalities (i.e. international normalized ratio (INR) ≥1.5 and/or platelets ≤50000)
• Local infection in the site of the block.
• Patients with body mass index (BMI) > 35.