The nature of the human mind is addressed from a neurological viewpoint. First from reported observations on subjects born blind with congenital cataract, who acquired vision after surgery, the concept of the primacy of somatosensation is developed. Therefrom some principles of the organization of higher sensory functions in the dominant parietal, occipital and temporal lobes are deduced. Sentience is traced to somatosensation. Some characteristics of the mind and of thinking are described. The non-existence of the unconscious is inferred. The question of free will is approached. Using neurological experience it is demonstrated that a good case for operation of a free will is difficull to establish. Positing the absence of a free will may be beneficial in the analysis and management of behavior. Finally the opportunity to study the nature and mechanism of the emotions in clinical neurology is outlined.

A 59-year-old man presented with the acute onset of paresthesias and pain in the left neck, face, and forehead. On subsequent investigation he was found to have a subadventitial type of carotid artery dissection, producing an ipsilateral Horner's syndrome with normal carotid angiography. MRI imaging of the neck structures, using fat saturation technique, showed the subadventitial dissection, sparing the vessel lumen. MRI offers a non-invasive method of diagnosis and follow-up for carotid artery dissection.

Cerebral vein thrombosis, also called superior sagittal sinus thrombosis, is a well recognized clinical and radiologic entity associated with a variety of medical disorders. We report a patient with fatal cerebral vein thrombosis following myelography, in whom the cause was familial antithrombin III (AT3) deficiency. Unsuspected AT3 deficiency should be considered in cases of unexplained cerebral venous thromboses.

Glutamate dehydrogenase (GDH), an enzyme central to glutamate metabolism, is significantly reduced in patients with heterogenous neurological disorders characterized by multiple system atrophy (MSA) and predominant involvement of the cerebellum and its connections. In human brain, GDH exists in multiple isoforms differing in their isoelectric point and molecular mass. These are differentially reduced in quantity and altered in catalytic activity in patients with clinically distinct forms of MSA, thus suggesting that these GDH isoproteins are under different genetic control. Dysregulation of glutamate metabolism occurs in patients with GDH deficiency and is thought to mediate the disease’s neurodegeneration via neuroexcitotoxic mechanisms. This possibility is supported by additional data showing that glutamate binding sites are significantly decreased in cerebellar tissue obtained at autopsy from MSA patients. At the molecular biological level, several cDNAs specific for human GDH have been isolated recently and cloned. Northern blot analysis of various human tissues, including brain, has revealed the presence of multiple GDH-specific mRNAs. In addition, multiple GDH-specific genes are present in humans and these data are consistent with the possibility that the various GDH isoproteins are encoded by different genes. These advances have laid the groundwork for characterizing the human GDH genes and their products in health and disease.

An association exists between antiphospholipid antibodies and chorea. As these antibodies are associated with thrombosis, it has been suggested that cerebral infarction might cause chorea. However, CT and MRI typically do not demonstrate focal basal ganglionic lesions in such patients and an autoimmune mechanism for chorea has also been proposed. We report a young woman with left hemichorea and dyspnea. She was found to have lupus anticoagulant, large aortic and tricuspid vegetations, and pulmonary emboli. CT and MRI showed a small lesion in the head of the right caudate. In the presence of a definite cardiac source for emboli (valvular vegetations) with embolic activity (pulmonary emboli), it is likely that this patient's hemichorea was caused by cardioembolic caudate infarction.

A patient presented with myelopathy due to intramedullary thoracic spinal cord glioblastoma 10 months after treatment for a supratentorial glioblastoma. There was no supratentorial recurrence, and no evidence of gross leptomeningeal dissemination documented by CSF cytology, complete myelography, and MR1 imaging. Gross examination of the spinal cord and arachnoid at the time of exploratory thoracic spinal surgery was normal. However, histological review of thoracic arachnoid demonstrated microscopic deposits of glial fibrillary acidic protein (GFAP) positive tumour consistent with malignant astrocytoma. Intramedullary spinal cord metastasis of cerebral glioblastoma rarely occurs, but may develop in association with leptomeningeal tumour dissemination. As local control of primary tumours improves, distant metastasis is likely to become a more common clinical problem. Leptomeningeal gliomato-sis may be very difficult to document, even when clinically suspected and GFAP staining of a biopsy of arachnoid tissue can play an important role in confirming the diagnosis. This information can be critical to establish prognosis and develop an appropriate treatment strategy.

Paraneoplastic cerebellar degeneration is a rare complication of a number of cancers, particularly small cell lung cancer, gynecologic cancers and Hodgkin’s disease. The disorder is clinically characterized by rapid development of pancerebellar dysfunction, which usually does not improve, and pathologically characterized by loss of Purkinje cells with or without inflammatory infiltrates. In some but not all patients, an autoantibody that reacts with the tumor and Purkinje cells can be found in the serum and spinal fluid of patients with paraneoplastic cerebellar degeneration. The presence of the autoantibody suggests, but does not prove, that the disorder has an autoimmune mechanism for its pathogenesis.

After just completing his neurosurgical training in 1954 Dr. William Horsey visited Queen Square, England, where on one occasion he attended a pathological conference discussing a young man who had died from complications following biopsy of a low grade astrocytoma. One of the surgeons present, none other than the brilliant, mercurial and sometimes flamboyant Wylie McKissock, asked young Horsey what he thought of the case. What followed was not the primitive, colonial opinion that might have been expected. Unintimidated, Dr. Horsey said that he probably would not have operated on the man in the first place, since he was neurologically well-preserved bearing an intrinsic tumor causing minimal deformity of the ventriculogram. But if he had operated, Horsey went on, he would have finished the job with a proper decompression of the affected temporal lobe, rather than just a biopsy. And, he continued, if he had made the decision to treat this young man's tumor, he would also have treated his postoperative clot, with a second operation, to save the patient's life. It was this kind of sharp intelligence and sensibility, which so silenced a crowded Queen Square conference room that morning, combined with a superb operating technique and a particular dedication to teaching that characterized Bill Horsey's neurosurgical career.

Neuropathic pain is not well understood. Although central dorsal horn remodelling is likely important in maintaining chronic neuropathic pain, afferent activity from injured nerves or ganglia may initiate these changes. It is suggested, in this review that the peripheral nerve trunk is capable of sustaining a “flare” response as observed in injured skin and other tissues. The injury response may be associated with local vasodilatation, plasma extravasation and the generation of painful local afferent activity sustained by locally originating peptidergic fibers (nervi nervorum). These fibers contain substance P, calcitonin gene-related peptide and other peptides that have been linked to nociceptive transmission. Manipulation of the local injury response of the nerve trunk by pharmacologic means may provide one strategy in the treatment of neuropathic pain.

Cerebellar ataxia is a common presenting sign in the Wernicke-Korsakoff syndrome (WKS). Recovery from ataxia following thiamine treatment is rarely complete, suggesting the existence of both a reversible (“biochemical”) lesion as well as irreversible, neuropathological damage. Cerebellar pathology in WKS includes severeloss of Purkinje cells in superior cerebellar vermis as well as neuronal loss from the granular layer. In addition, damage to inferior olivary nucleus could result in loss of climbing fibre input to cerebellum in this condition. Experiments using an animal model of WKS, the pyrithiamine-treated rat, reveal selective reversible decreases of α-ketoglutarate dehydrogenase (αKGDH) in cerebellum. Decreased enzyme activities are associated with decreased cerebellar content of GABA and aspartate. Thiamine reversal of neurological symptoms results in normalization of cerebellar enzyme activities and GABA content suggesting that reduced activities of αKGDH constitute “the biochemical lesion” in these animals. Possible mechanisms implicated in neuronal cell death in cerebellum include impaired cellular energy metabolism, focal lactic acidosis and excitotoxic damage resulting from excess glutamate release mediated by Nmethyl-D-aspartate (NMDA) receptors. Similar mechanisms could be involved in the reversible and irreversible neurological symptoms of WKS in humans.

In a patient receiving intrathecal baclofen injections for intractable trunk and leg spasms, positioning the subarachnoid catheter tip just caudal to the spinal segments innervating the spastic muscles enhanced the spasmolytic effect of bolus injections of intrathecal baclofen on the affected muscles. Such selective positioning of subarachnoid catheters may facilitate segmental spasmolysis with lower intrathecal doses of baclofen and provide an important alternative to relying only on ascending CSF concentration gradients of baclofen from chronic lumbar intrathecal infusion.