Sometimes the patient has unpleasant sensations of varied character, even though the principal pain for which the operation was carried out has been relieved. This occurs particularly when accompanying pain has not completely disappeared. These sensations are of long duration, and in some cases are permanent. Stabbing, electric, burning, unpleasant dull, and cold sensations have been described. In general, however, the incidence of these unpleasant side-effects is very small. In the literature one finds reference to between 0.5—8.6% (Sjoquist). We have not observed such side-effects in our own cases.
The operative risk per se is small, even though the procedure is often carried out on patients in poor condition from their basic disease, e. g. malignant growths, and with pain of long duration, which increases operative risk. Present-day mortality has fallen from an initial 25% to 4%. Of fifteen cases of our own, one died of his basic disease (6.6 %). Permanent effects of this operation depend on whether insensitivity to pain persists in the upper limits of the pain area, or even below it. With the descent of this border, the old pain begins to return.
Myelotomy of the posterior commissure (Goldwin-Greenfield-Armour, 1926) has been used mainly by the Lyons school (Leriche, Wertheimer). It has the same function as anterolateral chordotomy in interrupting crossover pathways of the spinothalamic tracts, in the anterior commissure of the greymatter of the cord, to an extent of two segments. This operation is mainly utilised for pelvic pain. It is less sparing of the tissue of the cord, since it also sections pathways which are not associated with pain. Justification for this is that at times it is impossible to rotate the cord due to adhesions of the arachnoid, which tend to immobilise the cord and thus prevent anterolateral chordotomy. Posterior myelotomy then remains the only possibility of achieving the desired end. It can also be used with advantage for simultaneous interruption of the spinothalamic tracts in those cases where the character and extent of the pain give rise to apprehension that a pain, which appears to be unilateral, might become bilateralised after a unilateral intervention. This may occur with malignancies of the uterus, appendix and bladder. The operation is carried out on the cord, which is mobilised to a length of 6 cm (Plate V). On the posterior surface, the midline is located, indicated by a vein in the posterior groove. This groove is not always clear, and the vein tends to run a slightly tortuous course, sometimes firmly adherant to an altered arachnoid on the surface of the cord. This vein must be very carefully freed and retracted. It is not always possible to carry this out, and the centre point of the posterior surface may have to be located by precise calculation, i. e. geometrically. It is advisable to drop blood or methylene blue on the posterior surface of the cord, the former then rolls into the central groove, but this is not always so easy in actual practice. Then, with a sharp scalpel, an incision is made through the entire thickness of the cord, i. e. 10—14 mm, and extended for at least 2 cm, in order to interrupt crossover fibres of the spinothalamic tract. This procedure is painful, and it is therefore necessary to anaesthetise the patient. Spinothalamic pathways are interrupted bilaterally. The operation is more severe for the patient than the above procedure and is accompanied by the danger of hypotension. The results of the operation are about the same as with anterolateral chordotomy. I have no particular experience with this operation, having carried it out on four occasions, not being satisfied with the results of anterolateral chordotomy. The two operations, therefore, followed in close succession. I have not found reports of undesirable after-effects in the literature, though I do not doubt that these effects exist, and I think will have quite another character from the after-effects of interruption of the anterolateral commissure. Further experience must be acquired.