One man's recollection of 50 years of functional and stereotactic neurosurgery.

The author summarizes personal recollections of his training and career in stereotactic and functional neurosurgery from the 1950s until his retirement from active surgery in 1999.

Tremor cells in the human thalamus: differences among neurological disorders.

OBJECT: Thalamic neurons firing at frequencies synchronous with tremor are thought to play a critical role in the generation and maintenance of tremor. The authors studied the incidence and locations of neurons with tremor-related activity (TRA) in the thalamus of patients with varied pathological conditions-including Parkinson disease (PD), essential tremor (ET), multiple sclerosis (MS), and cerebellar disorders--to determine whether known differences in the effectiveness of thalamic stereotactic procedures for these tremors could be correlated to differences in the incidence or locations of TRA cells. METHODS: Seventy-five operations were performed in 61 patients during which 686 TRA cells were recorded from 440 microelectrode trajectories in the thalamus. The locations of the TRA cells in relation to electrophysiologically defined thalamic nuclei and the commissural coordinates were compared among patient groups. The authors found that TRA cells are present in patients with each of these disorders and that these cells populate several nuclei in the ventral lateral tier of the thalamus. There were no large differences in the locations of TRA cells among the different diagnostic classes, although there was a difference in the incidence of TRA cells in patients with PD, who had greater than 3.8 times more cells per thalamic trajectory than patients with ET and approximately five times more cells than patients with MS or cerebellar disorders. CONCLUSIONS: There was an increased incidence of TRA in the thalamus of patients with PD. The location of thalamic TRA cells in patients with basal ganglia and other tremor disorders was similar.

Cranial root injury in glossopharyngeal neuralgia: electron microscopic observations. Case report.

Optical and electron microscopic examinations were made of a biopsy sample of the ninth and 10th cranial nerves obtained during posterior fossa surgery for the relief of pain in a patient suffering from glossopharyngeal neuralgia (GN). Pathological findings, which were restricted to a small fraction of fascicles in the nerves, included large patches of demyelinated axons in close membrane-to-membrane apposition to one another and zones of less severe myelin damage (dysmyelination). These observations, in the light of similar morphological changes observed in biopsy samples excised from patients with trigeminal neuralgia, and new information on the pathophysiological characteristics of injured peripheral nerve axons, can account for much of the symptomatology of GN.

Pathways involved in thalamic ventrobasal stimulation for pain relief: evidence against the hyphotesis VB stimulation - rostroventral medulla excitation - dorsal horn inhibition

A despeito de seu uso há longo tempo, a maneira pela qual a estimulaçäo talâmica ventrobasal (VB) produz alívio da dor é ainda desconhecida. Segundo uma das hipóteses mais aceitas, defendida por Tsubokawa dentre outros, a estimulaçäo de VB excita neurônios rafe-espinhais e eticulo-espinhais do bulbo rostroventral, os quais por sua vez emitem respectivamente axônios serotoninérgicos e noradrenérgicos inibitórios para os neurônios nociceptivos de ambos os cornos dorsais através dos funículos dorsolaterais da medula espinhal; essa via é a mesma proposta para a inibiçäo dos neurônios nociceptivos dos cornos dorsais pela estimulaçäo da substância cinzenta periventricular-periaquedutal (PVG-PAG). Tal hipótese, obviamente, subentende a necessidade da integridade dos funículos dorsolaterais da medula; de fato, já foi demonstrado que a secçäo desses funículos inibe a resposta dos neurônios nociceptivos dos cornos dorsais à estimulaçäo de VB. Se a hipótese mencionada for correta, poder-se á esperar que: (1) a estimulaçäo unilateral de VB produza alívio bilateral da dor (2) a estimulaçäo de VB e PC e PVG-PAG sejam úteis para tratar as mesmas modalidades de dor; (3) a estimulaçäo de VB seja ineficaz em pacientes com secçäo medular completa apresentando dor central de origem medular. Para se avaliar essas possibilidades, foram revistos os pacientes com dor central de origem medular admitidos à Divisäo de Neurocirurgia do Toronto Hospital entre junho 1978 e julho 1991 para serem submetidos à estimulaçäo cerebral profunda. Dezesseis pacientes foram operados nesse período, quatro dos quais apresentavam lesöo medular completa, segundo critérios clínicos. Todos eram homens, com média de idade de 48 anos e com dor secundária e traumatismo raquimedular. A eficácia da estimulaçäo cerebral profunda foi avaliada nesse subgrupo de pacientes: 75 por cento deles (3 dentre 4) apresentaram excelente alívio da dor à estimulaçäo de VB; a estimulaçäo de PVG, porém, realizada em três desses quatro pacientes, foi ineficaz em todos eles. Além disso, a experiência clínica tem demonstrado que a estimulaçäo unilateral de VB só é eficaz para o tratamento de dor contralateral. Esses resultados, bem como certos achados experimentais fornecidos pela revisäo da literatura, parecem prover evidência suficiente para contestar a hipótese de Tsubokawa

Abnormal single-unit activity recorded in the somatosensory thalamus of a quadriplegic patient with central pain.

We have performed single unit analysis of the activity of cells located in the ventral nuclear group of thalamus in a patient with dysesthetic pain below the level of a clinically complete traumatic spinal cord transection at C5. Cells located in the parasagittal plane 14 mm lateral to the midline responded to tactile stimulation in small facial and intraoral receptive fields, which were characteristic of patients without somatosensory abnormality [30]. In this patient the 16 mm lateral parasagittal plane contained cells with receptive fields located on the occiput and neck instead of the upper extremity as would normally be expected. Cells with receptive fields on the neck and occiput had not previously been observed in recordings from single units (n = 531) responding to somatosensory stimulation [30]. Thus, on the basis of their location in a region of thalamus which normally represents parts of the body below the level of the spinal cord transection and their unusual receptive fields adjacent to these same parts of the body, we propose that the cells in the 16 mm lateral plane have lost their normal afferent input. Analysis of the autopower spectra of spike trains indicates that cells in the 16 mm lateral plane exhibited a higher mean firing rate and greater tendency to fire in bursts than cells in the 14 mm lateral plane (P less than 0.005). Finally, electrical stimulation at the recording sites in the 16 mm lateral plane evoked a burning sensation in the occiput, neck and upper extremity. These results suggest that regions of thalamus which have lost their normal somatosensory input contain neurons which exhibit abnormal spontaneous and evoked activity and that electrical stimulation of these regions can produce the sensation of burning dysesthesia.