Alcohol, nerve block

In one study of 82 patients over a 20-year period who received repeated peripheral alcohol nerve blocks for trigeminal neuralgia, although moderate swelling and discomfort were invariable, significant complications occurred in only three of 413 nerve blocks (10) ... 

Nerve compression can be relieved by local corticosteroid (prednisolone) or nerve block (local anaesthetic) nerve destruction can be achieved by alcohol, phenol. 

Peripheral nerve block is created by injecting ethanol around the selected nerve. The effect of alcohol on nerve tissue has been examined in animal models and in postmortem specimens from patients who received neurolytic blocks (8,9). In general, alcohol causes destruction of nerve fibers, with subsequent Wallerian degeneration. The basal lamina around the Schwann cell usually remains intact. This leaves a tract available for axon regeneration without the formation of a neuroma. If the cell bodies are completely destroyed, regeneration will not occur. Contact of alcohol with unintended nerve roots underlies many of the more serious complications. Involvement of anterior rootlets sufficient to interrupt motor nerve function will result in muscle weakness or paralysis. Interruption of... 

Parenteral products containing up to 50% of alcohol (ethanol 95 or 96% v/v) have been formulated. However, such concentrations can produce pain on intramuscular injection and lower concentrations such as 5-10% v/v are preferred. Subcutaneous injection of alcohol (ethanol 95% v/v) similarly causes considerable pain followed by anesthesia. If injections are made close to nerves, neuritis and nerve degeneration may occur. This effect is used therapeutically to cause anesthesia in cases of severe pain, although the practice of using alcohol in nerve blocks is controversial. Doses of 1 mL of absolute alcohol have been used for this purpose. ... 

In tumors involving the lower third of the mediastinum, it is necessary to block the splanchnic nerves which contribute an important sensory nerve supply to the lower third of the intrathoracic part and the abdominal portion of the esophagus. The other indications are similar to those for celiac plexus block and splanchnic nerve block is preferred to celiac block in cases with large infiltration and invasion of periaortic space. The splanchnic nerve block requires a smaller volume of alcohol (Bonica 1990b Kurdziel and Dondelinger 1990 Herpels et al. 1988 Crespy et al. 1984 Lillemoe et al. 1993). 

Medicinally, cocaine is of value as a local anaesthetic for topical application. It is rapidly absorbed by mucous membranes and paralyses peripheral ends of sensory nerves. This is achieved by blocking ion channels in neural membranes. It was widely used in dentistry, but has been replaced by safer drugs, though it still has applications in ophthalmic and ear, nose, and throat surgery. As a constituent of Brompton s cocktail (cocaine and heroin in sweetened alcohol) it is available to control pain in terminal cancer patients. It increases the overall analgesic effect, and its additional CNS stimulant properties counteract the sedation normally associated with heroin (see page 332). 

The applications of computer tomography (CT)-guided interventions range from precise neurolytic block (neurolysis) of somatic spinal nerves and neurolytic sympathetic blockade to tumor alcoholization and percutaneous cementoplasty (Kanpolat et al. 1990 Gangi et al. 1994a Quinn et al. 1988). 

Regional analgesia with neurolytic blocks (neurolysis) achieved by injection of alcohol or phenol involves the intentional destruction of a nerve or nerves to interrupt nociceptive pathways for weeks or months (Ferrer-Brechner 1989 Filshie 1988 Lipton 1989 Oran 2001). It is essential to inform the patient of the details, the benefits, and any side effects that might occur with the block technique. 

Fig. 11.1. Pancoast s syndrome with major cervical spine invasion in a patient with excruciating pain in the upper limb. A 22-gauge needle was introduced just lateral to the transverse process of the affected vertebra under CT guidance. The spinal nerve lies in the sulcus of the transverse process. Brachial plexus block was performed at C5 and C6 level. Slight weakness of the limb after alcoholization. Good pain relief was obtained lasting until death of the patient 6 weeks later...

Block of the plexus or major nerves of the upper or lower limb with larger volumes of alcohol results in paresis or even total paralysis and should not be considered except in such unusual cases as patients with excruciating pain not relieved with narcotics, and for whom neurosurgery is contraindicated. The effects and comphcations should be discussed with the patient in advance, particularly the risk of paresis or paralysis. Only when the patient has decided that the risk of paralysis is preferable to the severe pain... 

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