Metastasis to and from the central nervous system--the 'relatively protected site'

The brain has long been recognised as a site with a very low rate of metastases, despite the potential for cancers to be extremely locally aggressive. This feature contrasts with most of the rest of the body, where metastatic spread is much more common. The pathological behaviour of any tumour is governed by both its inherent composition and the composition of the matrix in which it is sited. Much work has been done in recent years to elucidate the factors within the central nervous system (CNS) that give the brain its unique properties. Tumour interactions with the blood-brain barrier, microglia, and various matrix proteins, cytokines, and growth factors have a central role. This review concentrates mainly on the process of tumour spread from the CNS and explores how the brain is a protected site. CNS metastases from extraneural sites are also briefly covered.

Self-trephination of the skull with an electric power drill

There is extensive archaeological evidence of the practice of trephination of the skull in many ancient cultures in different parts of the world. We report a case of self-trephination of the skull by a patient using an electrical power drill subsequently requiring neurosurgical intervention.

Intermittent claudication due to spinal stenosis in a vascular surgical practice

Intermittent claudication can be due to spinal canal stenosis. In order to define the frequency with which this condition presents to a vascular surgeon a review of 271 patients referred with claudication was carried out. Twenty-one (8%) were ultimately diagnosed as having spinal stenosis. There were no significant differences with regard to age or sex between these patients and those with true vascular claudication. There was, however, a significantly lower number of smokers in the spinal stenosis group. When the presenting features of the spinal stenosis group were analysed 62% (13/21) reported sensory symptoms such as numbness or parasthesiae, 38% (8/21) back pain and 67% (14/21) true pain in the legs on walking. In 71% (15/21), symptoms were reported as being bilateral and 29% (6/21) had reduced Doppler pressures. It is stressed that vascular surgeons need to maintain a high index of suspicion for spinal stenosis especially as the condition may coexist with vascular disease, making diagnosis difficult.

Stereotactic mesencephalotomy

Within the mesencephalon lie nuclear masses and fiber tracts that connect higher and lower portions of the neuraxis. The pathways subserving epicritic (discriminatory) sensation and protopathic (motivational) sensation are adjacent to one another and can be localized precisely with stereotaxy. Discrete thermal lesions overflowing between the direct spinothalamic and quintothalamic pathways laterally and the more diffuse ascending pathways medially can be created. By careful target selection the surgeon can avoid significant damage to adjacent structures and offer relief of central or malignant pain without substantial sensory disturbance. At the same time the emotional disturbances that often persist with other remedies are reduced. Intraoperative electrophysiologic monitoring may help minimize unwanted and distressing side effects. It is fortunate that nature has designed the upper brain stem in such a fashion to allow effective pain relief procedures. Although stereotactic mesencephalotomy is not a panacea, it offers relief of pain syndromes that cannot otherwise be helped while abolishing the associated emotional problems that otherwise can be relieved only by psychosurgical procedures.

Cutaneomeningo-spinal angiomatosis: the syndrome of Cobb. A case report

We present the case of a young patient with Cobb's syndrome who presented with an acute paraplegia. A review of the literature indicates that this condition is rare. The coexistence of cutaneous naevi in a dermatomal pattern and neurological signs of a spinal cord lesion is significant and should always be considered as the excision of spinal arteriovenous malformations can be accomplished safely.

Impedance measurements of the spinal cord of man and animals

The measurement of electrical impedance of normal and pathologic tissue has not been fully utilized in neurosurgery. This is a report of electrical impedance measurement in the central nervous system of both man and animals. We show the results of the laboratory study done in animals, in the brain and in the spinal cord as well. Also we show the clinical experience of the impedance recordings in the DREZ procedure for some chronic pain conditions, correlating the measurements at the time of the operation with normal conditions, with comments about the findings.

Thalamic pain and stereotactic mesencephalotomy

The severe pain that can be experienced by stroke patients is refractory both to drugs and to non-medical therapies. Various surgical procedures are widely advocated for its relief, stereotactic mesencephalic tractotomy in particular providing good results. Twenty seven patients with pain of central origin following stroke underwent stereotactic mesencephalic tractotomy by thermocoagulation at one of two alternative sites. Fourteen had lesions created at the original target adjacent to the superior colliculus, 75% reporting long term relief of their pain. Of this group, 83% had residual postoperative ocular dysfunction (50% symptomatic) and two died soon after surgery. Thirteen patients had surgery at the revised target at the level of the inferior colliculus: 58% had long term pain relief, 23% had ocular problems (none symptomatic) and mortality was nil.

Stereotactic mesencephalic tractotomy for thalamic pain

Forty years after its first reported use, stereotactic mesencephalic tractotomy remains effective in relieving thalamic pain. Twenty seven patients suffering central pain following cerebrovascular accidents were treated by this operation and twenty four were reviewed: sixteen (66.7%) reported long term relief. Fourteen underwent surgery at the original 'superior colliculus' target, nine out of twelve (75%) reporting significant relief. Thirteen had surgery at a revised 'inferior colliculus' target, seven out of twelve (58.3%) obtaining relief. Postoperative disorders of ocular movement were reduced from 83.3% to 20%, and significant problems of binocular vision from 50% to nil. The mortality rate was 7.4%.

Stereotactic mesencephalic tractotomy for the relief of thalamic pain

Twenty-seven patients with pain of central origin following cerebral hemisphere or brain stem infarction underwent stereotactic mesencephalic tractotomy. Twenty-one (77.8%) were pain free or significantly improved at discharge. Twenty-four were available for later review and 1p (66.7%) reported relief up to 5 years later. The target site was revised after the first 14 patients, reducing the number obtaining long term relief (lesion I, at the level of the superior colliculus--75%; lesion II, at the level of the inferior colliculus--58.3%), but substantially decreasing the incidence of disorders of ocular function from 83.3% to 16.7%.

Electrical impedance recording for localization in functional neurosurgery of the spinal cord and lower brain stem

Functional neurosurgery aims to modify or abolish neural messages. Established techniques use confirmatory electrical stimulation prior to ablation and require local anesthesia. Recently developed procedures take place under general anesthesia increasing the chance of damage to adjacent neural structures with postoperative morbidity. We describe a laboratory study correlating changes in measured electrical impedance with transition from white to grey matter in the brain and spinal cord of two mammalian species; this has not previously been easy to undertake, nor felt reliable. Impedances can now be measured simply and reliably. This study confirms our operating theater experience. We recommend that when stimulation cannot be used, impedance can and should be utilized to indicate the need for an electrode to be resited.