Subarachnoid phenol block in the treatment of pain and spasticity

Abstract

In 195:5, Maher in England first described the use of subarachnoid injections of phenol solutions in the treatment of intractable pain resulting from cancerl. Since then, numerous investigators have confirmed the efficacy of this procedure for treatment of severe pain problems and for relief of spasticity due to various neuro logic conditions. 2-11 Our experience with the first 43 patients whom we have treated with subarachnoid phenol blocks for pain and spasticity is reported in this article.PROPERTIE S OF PHENOL Carbolic acid or phenol is a weak acid (KA = 1'7 x 10-10) with bactericidal and caustic properties. Phenol is used in various preparations and concentrations as a topical analgesic, antipruritic, disinfectant, or cauterising agent; and is used in injectable form to destroy or attenuate nerve function, and to produce fibrosis about ligaments (prolotherapy). Lipid solutions of phenol dissolved in glycerin or ethyl iodophenylundecylate (Pantopaque)* are less caustic than aqueous phenol solutions. The effect of 5 per cent. lipid solution upon nerve fibres is approximately the same as an 0'1 per cent. aqueous solution.l2 To cause permanent destruction of all nerve fibres, a 25 per cent. lipid-phenol solution is required;' Animal experiments have shown that there is a differential blocking effect of phenol solutions upon the various action potentials of nerve roots. The function of small nerve fibres-the gamma fibres which mediate spasticity and the 'C' fibres which mediate pain-is more severely and more permanently impaired by exposure to various concentrations of phenol than are the larger nerve fibres.12,13 This differential effect of phenol-relief of pain and spasticity with minimum involve ment of voluntary motor activity and sensory perception-is one basis of its unique clinical value. Histologic studies on animals and patients, however, have shown that nerve fibres of all sizes show a similar degree of myelin degeneration following exposure to a phenol solution. Thus, the differential physiologic effect of phenol upon nerve function does not correspond to results of the pathological examin ation.l4,l5.l6 Post-mortem examinations of humans have occasionally shown evi dence of arachnoiditis in the area of phenol application, but no clinical systemic or meningitic reactions (as have been noted following subarachnoid alcohol blocks) have been reported. CLINICAL PROBLEMS AND TREATMENT OFSPASTICITY AND PAIN Spasticity and pain are two major problems in the rehabilitation of patients with injury or disease of the central nervous system. Spasticity itself frequently causes pain. Furthermore, muscle spasticity interferes with movement, predis-* Pantopaque is the Lafayette Pharmaceutical Company trade name for iodophenyl undecylate.

Pharmacological management of spasticity in multiple sclerosis: Systematic review and consensus paper

“…[95][96][97][98] Two case series reported descriptive results in terms of general relief of spasticity (class IV evidence). 95;96 A cross-sectional observational study compared an initial phenol injection (initial group) versus subsequent injections (serial group) in five muscle groups, in both targeted and non-targeted sides, showing a significant reduction in the Ashworth score in both groups.…”

“…No randomized controlled trials evaluating the effect of intrathecal phenol on spasticity due to MS or other causes were identified and four observational studies were reviewed. [96][97][98][99] Two case series reported descriptive results in terms of general relief of spasticity (class IV evidence). 96,97 A cross-sectional observational study compared an initial phenol injection (initial group) versus subsequent injections (serial group) in five muscle groups, in both targeted and non-targeted sides, showing a significant reduction in the Ashworth score in both groups 98 (class IV evidence).…”

Treatments for spasticity and pain in multiple sclerosis: a systematic review

“…80 Peripheral nerve blockade other than the obturator nerve (which supplies a very small area of skin, and that is partially supplied by other nerves) is reported to result in anaesthetic skin and sometimes persistent severe pain. 81 Arachnoiditis and sphincter dysfunction following intrathecal injection are also referred to.…”

“…Two of the case series do include case examples, 80,81 but there is no indication that these are typical of all the cases.…”

Paraplegia after intercostal neurolysis with phenol

“…(The use of phenol solutions in water may result in 50 times higher toxicity than that of lipid phenol. )13…”