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Biomedical subjects

W H Sweet

Publications and source records attributed to W H Sweet.

At least 37 records · Page 2Linked to original sources
PubMed1984

Deafferentation pain after posterior rhizotomy, trauma to a limb, and herpes zoster.

After incisional or alcoholic destruction of trigeminal posterior rootlets, constant dysesthesias of major degree referred to some part of the markedly denervated zone develop in 5 to 15% of the patients. The full severity may not appear for weeks or months. There is no allodynia or hyperpathia of the denervated zone. Bulbar trigeminal tractotomy with sparing of touch sensation produces severe dysesthesias in a tiny percentage of the patients, as does selective destruction of pain fibers by radiofrequency heating or glycerol. Spinal posterior rhizotomy elicits in less than 4% a lasting dysesthesia entirely different in temporal sequence, locus, and type of pain: (a) it tends to be maximal early after operation and to improve, (b) the spontaneous pain is accompanied by severe allodynia, and (c) the pain is usually referred beyond the margins of the insentient (rhizotomized) zone and may even be referred to the corresponding area on the opposite side. Sindou's "selective posterior rhizotomy," i.e., cutting of the small fiber lateral component of each rootlet as it enters the cord, has not given rise to dysesthesias. These do occur briefly in 50% of the cases following spinal ganglionectomy, the sensations being referred to the dermatomal segment of the ganglion in question. The secondary afferent neurons in the mesencephalic, principal, oral, and interpolar nuclei for the trigeminal posterior roots have no counterpart in the spinal cord for the spinal posterior roots. We suggest that the explanation for the fact that neither trigeminal neuralgia nor trigeminal anesthesia dolorosa have a spinal clinical counterpart is related to the as yet unexplained special functions of the elaborate trigeminal secondary afferent neuronal apparatus.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1982

Conducted somatosensory evoked potentials during spinal surgery. Part 2: clinical applications.

In 27 patients undergoing laminectomy, spinal cord function was monitored by epidural bipolar recordings of conducted spinal somatosensory evoked potentials (SEP's) across the laminectomy site, with calculation of spinal conduction velocity (CV). In control cases without myelopathy, the CV remained relatively constant (+/- 3%) even during prolonged operations, despite markedly changing levels of anesthesia. Acute CV changes were detected intraoperatively in three cases: these patients displayed improvement after extramedullary (Case 1) and intramedullary decompression (Case 2), and deterioration after direct unilateral dorsal column injury (Case 3). These intraoperative CV alterations correlated postoperatively with changes in the neurological examination. Although a unilateral lesion confined to the dorsal column abolished the ipsilateral SEP in Case 3, complete anterior quadrant lesions did not consistently change the CV (Case 4). This further suggests that the SEP is generated entirely by ipsilateral dorsal column activation. Accurate measurement of this dorsal column conduction velocity across the operative field provides a very sensitive means of monitoring spinal cord function during operations for neurosurgical spinal lesions.

Aged↗
PubMed1981

Treatment of trigeminal neuralgia and other facial pains by retrogasserian injection of glycerol.

Håkanson's treatment of trigeminal neuralgia by injecting 0.2 to 0.4 ml of glycerol into the cerebrospinal fluid in Meckel's cave was carried out in 27 patients with trigeminal neuralgia, 3 with atypical facial neuralgia, and 1 with post-traumatic facial neuralgia. Minor modifications of his technique are described based on our finding of a greater pain and sensory loss upon injection than he noted. We present evidence that glycerol is more toxic than its cryoprotectant effect would intimate and that it selectively eliminates those components of the compound action potential in the trigeminal rootlets customarily associated with pain. We conclude that the method is probably going to be an improvement over radiofrequency heating for the treatment of trigeminal neuralgia in many situations.

Face↗
PubMed1981

Cancer pain relieved by long-term epidural morphine with permanent indwelling systems for self-administration.

Clinical trials for abatement of intractable pelvic cancer pain were conducted in two patients, each electing surgical implantation of one of two indwelling catheter systems for administration of morphine into the spinal epidural space. Both systems, one consisting of a partially indwelling Broviac catheter, and the other, completely indwelling, consisting of a morphine reservoir connected to a shunt pump and on-off Hakim valve assembly, permitted the patients to return home where they could self-administer epidural morphine. Each patient reported that 2 mg of epidural morphine provided 8 to 12 hours of pain relief at a level of superior to their previous narcotic medication. On a regimen of 2 mg of epidural morphine administered twice daily, both patients experienced analgesia for 6 months, unaccompanied by alterations in sensory, motor, or cognitive functioning, and with a little drug tolerance reaction.

Carcinoma↗
PubMed1980

Central mechanisms of chronic pain (neuralgias and certain other neurogenic pain).

Almost all supratentorial intracranial lesions which may effectively control chronic pain in man are ineffective for acute pain. There are at least 10 sites at which lesions producing no somatic sensory loss have often stopped the peculiarly agonizing chronic pain of advanced cancer. They include: (a) inferior posteromedial or subcaudate (preinnominate) frontal white matter; (b) supracallosal portion of cingulum; (c) thalamotomy of centrum medianum and parafascicularis nuclei; (d) thalamotomy of linear parasagittal type separating connections between lateral specific and medial nonspecific sensory relay nuclei; (e) thalamotomy of pulvinar; (f) amygdalotomy; (g) frontothalamic tractotomy; (h) hypothalamotomy-posteromedial nuclei; (i) hypothalamotomy-periventricular nuclei; (j) hypophysectomy. It is indeed remarkable that such diversely situated lesions may many times be so successful. We understand poorly the mechanisms by which this control is often (though at times only temporarily) achieved. Hence, we are in real need of animal models to permit critical analysis. The problem of devising an ethically acceptable modus operandi is formidable. However, an ethicist who would demand that every time an experimental animal is showing some distress the experiment must be terminated, must also bear some responsibility for continuing disabling pain in hundreds of thousands of people.

Amygdala↗
PubMed1979

Relative cerebral glucose metabolism evoked by dental-pulp stimulation in the rat.

Electrical stimulation of dental pulp is widely acknowledged to produce a sensation that is predominantly or exclusively noxious in character. The authors report the pattern of local cerebral glucose utilization evoked by dental-pulp stimulation in the barbiturate-anesthetized rat, using the [14C]2-deoxyglucose method of Sokoloff. Autoradiographs were prepared from cryostat-cut brain sections of animals given an intravenous pulse of [14C]2-deoxyglucose and sacrificed after 45 minutes of continuous bipolar stimulation of the incisor tooth pulp. Areas of high optical density on the autoradiographs identified brain regions where glucose consumption, and hence functional activity, was maximal. Stimulus-related increases in glucose utilization were seen ipsilaterally in an uninterrupted column from the lower levels of trigeminal nucleus caudalis to the rostral extent of the main sensory nucleus. Mandibular incisor pulp stimulation yielded increased deoxyglucose uptake in relatively restricted dorsal portions of the nuclei, while maxillary pulp stimulation produced a more extensive area of uptake ventrally. Elevated deoxyglucose uptake was also seen in the contralateral ventrobasal thalamus and sensory cortex with maxillary, but not mandibular, pulp stimulation. No changes in metabolic activity were detected in extralemniscal or limbic structures. These initial results suggest that the [14C]2-deoxyglucose method may be a useful means of mapping central structures involved in nociception.

Animals↗
PubMed1978

Brain death.

Explore the source record for details and available documents.

Brain↗
PubMed1976

Control of pain by direct electrical stimulation of peripheral nerves.

Our results after implanting electrodes around peripheral nerves in 69 patients over a 10 year period are only fair with but 17 individuals maintaining relief until death or until the present time. Thirteen others had weeks or months of temporary relief. A continuing use of transcutaneous and better still of percutaneous electrodes to guide the decision regarding implantation is almost certainly advisable. Intensive efforts in laboratory animal studies with models of chronic pain are needed to improve our understanding of exactly what we should be doing. Empirical sustained work with the individual patient is likely to improve the figures we have presented, even in our present state of ignorance.

Aged↗
PubMed1976

Radical surgical treatment of craniopharyngioma.

There is evidence from this publication and those of Matson and colleagues that a determined effort at total excision of these tumors as the initial therapy is a tenable course of action. The main bases for this concept are: (1) that the dense gliosis characteristically intervening between these epithelial tumors and normal brain constitutes a margin of safety for the surgeon at least for the first several years such tumors are growing in the 3rd ventricle; (2) improved early diagnosis and better operative instruments, magnification, lighting, and technique are decreasing operative morbidity and mortality; and (3) new knowledge and new replacement therapy are reducing the burden of the metabolic and endocrine defects. Competing with this is the concept that rotationally delivered or even more precisely focused high energy photons and intracavitary beta-radiation have lower morbidity and mortality. The detailed and long term data on which to draw conclusions are not yet available. My medical colleagues and I are preparing case-by-case tables with all of the relevant facts to supply one component of the total picture.

Adolescent↗