This paper describes the development and testing of a computer algorithm to automate the process of peak identification and somatosensory evoked potential (SSEP) grading. We tested the accuracy of computerized peak detection and evaluated grading schemes using a test set of 60 SSEPs ranked from worst to best by the programmer (RJM) and a blinded grader (PO). The computer algorithm recognized 95% of peaks identified by visual inspection. Twelve percent of peaks identified by the computer were noise. Summed peak to peak amplitude gave the most accurate ranking of SSEPs. Rank correlation between computer and blinded and unblinded expert grading was r = .82 for PO, r = .92 for RJM, p < .0001 for both. Computer and manually summed amplitudes were highly correlated (Pearson r = .98, p < .0001). Correlation between the 2 expert graders was .86, p < .0001. Computer graded SSEPs were significantly related to clinical outcome at 3 months, p < .0001. Automatic grading of SSEPs using summed peak to peak amplitude is highly correlated with expert grading. The measure is objective, continuous, and well suited to statistical analysis.

An in vitro model of muscle damage was used to investigate the protective effect of mild hypothermia in muscle injury. Rat epitrochlearis muscles were dissected in their entirety and suspended in Krebs-Ringer solution and DNP, a mitochondrial uncoupler, was added. PGE2, and lactate release and the contractile response to stimulation were measured and compared to untreated controls. Experiments were done at 37, 35, 33 and 27°C. At 37°C, DNP stimulated muscle releases large amounts of PGE2 and lactate and is unable to contract. As the temperature is reduced, there is progressive preservation of contractile force, although high lactate levels at the lowest temperatures indicate that the metabolic stress is still present. In contrast, DNP stimulated PGE2 release is completely inhibited at or below 35°C and may be related to a similar protective phenomenon seen in experimental ischemic neuronal death.

The purpose of this study was to explore the relationship between neurologic function, using a quantitative measurement of continuous somatosensory evoked potentials (SSEPs), and intracranial pressure (ICP) following traumatic brain injury. During a 6 year period, severely head-injured patients with a Glascow Coma Scale ≤ 8 who were not moribund were monitored with SSEPs and ICP measurements. SSEPs from each hemisphere and ICP were recorded hourly for each patient. Neurologic outcomes were scored using the Glasgow Outcome Scale at three months post injury. Although initial SSEP amplitude did not correlate well with outcome, final SSEP summed peak to peak amplitude from both hemispheres (p = .0001), the best hemisphere (p = .0004), and the worst hemisphere (p = .0001) correlated well with the Glasgow Outcome Scale groups. Of a total of 72 patients, 40 had deteriorating SSEPs and 32 had stable or improving SSEPs. Peak ICP values were not statistically different in these groups (p = .6). Among patients with deteriorating SSEPs, 52.5% lost the greatest proportion of hemispheric electrical activity prior to ICP elevation. In the remaining patients, the percent reduction of SSEP activity after peak ICP levels was not statistically different from the percent reduction in SSEP activity prior to the peak ICP levels (p = .9). This data suggests that in a select group of patients with severe head injury, ICP does not cause SSEP deterioration, but rather is the consequence of deterioration of brain function.

We explored the effects of chronic lumbar intrathecal NMDA infusion (mini-osmotic pumps) in Sprague-Dawley rats on motor and sensory axon integrity. Several different infusion protocols, each given over a 4 week period were examined: 0.15 M NMDA in phosphate buffered saline; phosphate buffered saline without NMDA; and 0.20 M magnesium sulfate plus 0.15 M NMDA; 0.35 M NMDA. In two additional protocols, 0.15 M NMDA or phosphate buffered saline were infused for a total of 8 weeks. Within 1-2 weeks of the onset of NMDA, but not phosphate buffered saline infusions, the rats exhibited irritability, circling, biting and excessive grooming resulting in loss of hair, and skin ulcerations from autotomy localized to lumbar and sacral innervated dermatomes. Co-infusion of NMDA with magnesium sulfate almost completely prevented these findings. The behavioural changes were not associated with abnormalities of sensory or motor conduction. Intrathecal infusion of NMDA induces a chronic “central” experimental pain disorder in rats, localized to the cord segment with the greatest exposure to the infusion, without involvement of peripheral sensory axons and sparing the axonal integrity of anterior horn cells.

We studied the electrophysiological changes occurring in six patients with tethered cord syndrome. Evidence of spinal malformations was provided by magnetic resonance imaging. The functional assessment of the spinal cord was performed by analysing both spinal and cortical somatosensory evoked potentials. The evoked electrospinogram was recorded from the thoracic and lumbosacral spinous processes. The N22 lumbosacral potential was selectively affected, being rostrocaudally displaced and reduced in amplitude or even absent in patients with neurological signs indicating a segmental lower cord lesion. Inter-peak somatosensory evoked potentials latency was normal in all cases, suggesting that ascending axonal potentials in the dorsal column fibres may be synchronized. Segmental potentials of the lumbosacral response, originating from the post-synaptic activity of dorsal horn interneurons, are selectively affected in this syndrome resulting from the rostrocaudal displacement of the spinal cord due to tethering. Our findings in the clinical field are consistent with previous experimental evidence indicating a different sensitivity of the gray vs. white matter to progressive stretching.

Five hundred and fifty-three patients were referred to a Canadian dementia clinic for standardized evaluation. The majority (83.5%) had a dementia with Alzheimer’s disease (AD) accounting for 89% of dementias. Patients with probable AD who were followed for five years had variable rates of progression, increased mortality (37.1%, 2.5 times the expected rate) and a high rate of institutionalization (79%). Simple demographic (age) and social factors (marital status) were strong predictors for institutionalization. It was extremely difficult at presentation to predict the rate of progression. The prevalence of AD in autopsied cases was 62.5%. Clinic patients were younger, had milder dementias, and were more likely to have AD than patients identified in the course of a contemporaneous population-based dementia prevalence study.

Guillain-Barré syndrome causes, in addition to paralysis and respiratory failure, many general medical problems that have great bearing on outcome. The main features of daily care that require attention are: respiratory and urinary tract infections, gastrointestinal dysfunction, hyponatremia, pain control, and the potential for pulmonary embolism. Dysautonomic problems that arise specifically in the intensive care unit include: hyper- and hypotension, cardiac arrhythmias, and ileus. Throughout the illness, certain psychological aberrations and communication problems must be addressed. The experience reviewed herein provides a practical approach to these problems.

Two siblings, a 35-year-old male and a 37-year-old female, offspring of first cousins, presented with a hereditary motor and sensory neuropathy with type I clinical features which began to manifest at about age 10 years. Nerve biopsy in the proband showed it to be a type characterized by excessive myelin outfolding. Morphometric study revealed hypomyelination with focal thickenings due to outfoldings. Clinical, electrophysiological and morphological findings are virtually identical to those described by Ohnishi et al. The peculiarity of the neuropathological picture suggests a particular form of hereditary motor and senory neuropathy.

Recent brain research proposes that, during ischemia, synaptically released excitatory amino acid neurotransmitters accumulate at toxic concentrations with ensuing neuronal death. Their action is mediated by the receptor subtype N-methyl-D-aspartate (NMDA). The protective effect of NMDA receptor blockade with intrathecal MgS04 and MK-801 was investigated during spinal cord ischemia induced by aortic occlusion of 12 minutes. Male Sprague-Dawley rats, 250-300g, underwent intrathecal administration of 20 μL of normal saline (SA n = 16), MgS04 1M (MG n = 16), or MK-801, 25 mM solutions (MK n = 16) in a randomized order. After 2 hours, the animals underwent occlusion of the thoracic aorta and subclavian arteries for 12 min. An additional control group (CO n = 16) underwent occlusion for 12 minutes, without intrathecal injection. The animals were scored according to their functional performance (LS = lesion score) each day for four days by a blinded observer. Mean LS were calculated for each group at a given day. Treatment and control groups were not different at day 1 (P = 0.302). Group MG was improved from groups SA (P = < 0.0039) and CO (P = < 0.0048) at day 4. This study demonstrates that although intrathecal NMDA receptor blockade with MgS04 or MK-801 does not prevent paraplegia due to spinal cord ischemia in the rat, it could however influence the rate of recovery after ischemic injury.

Consecutive patients (n = 114), who had single fiber electromyography of the frontalis muscles for symptoms suggestive of ocular myasthenia gravis, were followed up for a mean of 14 months (3-64 mos). At follow up, based on strict criteria, 23 patients were classified as having ocular myasthenia gravis, 8 patients were diagnosed as having mitochondrial myopathy or oculopharyngeal dystrophy, 18 patients were found to have other diseases and 65 patients remained without a definite diagnosis. The single fiber electromyography data of these patients were then reviewed. The patients with ocular myasthenia gravis had, on average, more than 7/20 single fiber pairs with jitter > 45 μs and mean jitter of 56 μs. The 8 patients with mitochondrial myopathy or oculopharyngeal dystrophy had an average of 5/20 single fiber pairs with jitter > 45 μs and a mean jittter of 52 μs and could not be separated from the group with ocular myasthenia gravis on the basis of the single fiber electromyography results. The 18 patients with definite other diagnosis had an average of less than 1/20 single fiber pair with jitter > 45 μs and a mean jitter of 25 μs. This group could be clearly separated from the group with ocular yasthenia gravis. We conclude that single fiber electromyelography is useful in the separation of ocular myasthenia gravis from other causes of oculomotor weakness except mitochondrial myopathy and oculopharyngeal dystrophy.

We compare complications from 66 sural nerve biopsies in 41 patients with diabetic peripheral neuropathy to 40 patients with neuropathy from other causes, using a retrospective telephone survey. Diabetic patients were followed for a mean of 6.8 years and non-diabetics for 5.6 years. Mild long-term pain was described by 18.9% of patients overall with no difference between groups. Mild persistent sensory symptoms, insufficient to interfere with daily activity or warrant medical therapy, were reported by 63.6% of diabetic and 27.5% of non-diabetic patients (p < 0.006). Wound infection and severe pain were uncommon in both groups and no different in diabetics. Significant complications of sural nerve biopsy occurred no more frequently in diabetic than in non-diabetic patients. While sural nerve biopsy plays no role in the routine evaluation of diabetic peripheral neuropathy, it may be performed without increased risk when indicated in these patients to exclude other causes of neuropathy and in the context of research trials.

The organization of the primary somatosensory cortex innervated by the ulnar nerve was studied before and immediately after ulnar nerve transection in 11 cats electrophysiologically mapped under Nembutal or Ketamine anesthesia. The cortex was reexamined a second time beginning 42 hr after nerve transection in four cats anesthetized with Nembutal. One additional sham-operated control was also mapped. The region of cortex formerly served by the ulnar nerve remained largely unresponsive to somatic stimulation independent of the type of anesthetic used during recording. Nonetheless, animals anesthetized with Ketamine had more new responsive sites in deafferented cortex following nerve cut than cats anesthetized with Nembutal. New responses, when observed, were evoked by stimulation of a region of skin adjacent to the region served by the ulnar nerve. These findings suggest that the immediate response to deafferentation of somatosensory cortex is a limited acquisition of novel responses restricted to a region immediately adjacent to cortex containing normal afferent input.

Disorders of both the central and peripheral nervous systems are important causes of respiratory insufficiency. However, simple clinical observations and pulmonary function measurements may fail to identify the location and type of disorder. This can often be accomplished by the newly-developed technique of phrenic nerve conduction and needle electromyography of the diaphragm which delineate the various disturbances of central drive, axonal or demyelinating neuropathies of the phrenic nerves and certain myopathies. These studies have been preformed safely and with little discomfort on adults, children or infants, and in out-patient and general ward settings. We have found they are of particular value in the intensive care unit.

A retrospective review was undertaken of 139 consecutive patients with presumed carotid artery stenosis referred to a vascular neurosurgeon. The review period included three years prior and one year subsequent to the publication of the North American Symptomatic Carotid Endarterectomy Trial (NASCET) preliminary results showing surgery to be superior to best medical therapy for patients with symptomatic, high grade (> 70% linear diameter) carotid stenosis. The aims of this analysis were to determine any changes in the referral pattern following the NASCET publication (post-NASCET), and to examine the use and reliability for surgical decision making of pre-referral carotid artery imaging. Patient referral rate increased markedly post-NASCET, particularly from neurologists. There was a trend for more post-NASCET referrals to be for high grade stenosis and fewer referrals to be for intermediate grade (30-69% linear diameter) stenosis, although continued referral of patients with intermediate grade stenosis is desirable as randomization into NASCET continues for this group of patients. Ninety-six patients (69%) were referred with carotid duplex ultrasonography having been performed. There was poor correlation of these results with angiography, which remains necessary for planning management. A majority of patients (65%) referred to this surgical practice did not come to surgery.

Twenty-six of 95 adults treated for tuberculous spondylitis, between 1982 and 1993, underwent surgery. Twenty-one exhibited neurological deficits: radicular deficits: 4, and progressive spinal cord syndromes: 17 (incomplete: 13, complete, of acute onset: 4). Vertebral body compression fracture was the most prominent finding. Indications for surgery were neurologic: 11, mechanical: I, etiologic: 1, and mixed: 13. Twelve patients had vertebrectomies, 3 laminotomies and 11 laminectomies. The average follow-up was 23 months. The neurological recovery was complete in 16 cases, partial in 4 cases and unchanged in one case. Bony consolidation occurred after 3–5 months. The medicosurgical treatment produced a very high cure rate, so rapidly, that it became the treatment of choice in our setting. Moreover, that allows to specify the diagnosis. Anterior decompression and fusion is recommended in the cervical and lumbar spine. In the thoracic segment, significant kyphosis is infrequent, so that surgical correction is rarely necessary. Laminotomy may occasionally be indicated for posterior decompression for abscess. Laminectomy is now preferred for uncommon cases of thoracolumbar posterior compression by tuberculous arachnoiditis or associated posterior vertebral tuberculosis. Indications for open biopsy are discussed.

The prognostic value of magnetic resonance imaging (MRI) in the syndrome of acute transverse myelitis had not been evaluated. After retrospective study of 14 cases, we found that MRI is valuable for both diagnosis and prognosis in this illness. The criteria for the diagnosis of acute transverse myelitis consisted of acute onset (over less than 3 weeks) of symmetrical motor and sensory dysfunction referable to a distinct spinal cord level, with sphincter dysfunction. Patients with abnormal MRIs of the spinal cord had significantly worse outcomes than patients with normal MRIs.

The ability to analyze the genotype of deceased affected members of pedigrees segregating inherited neurological diseases considerably augments the informativeness of such pedigrees. This information has direct application in attempts to isolate disease genes by positional cloning strategies, and for genetic counselling. We show that the genotype at polymorphic simple sequence repeat loci can be determined from genomic DNA isolated from 10 micron thick paraffin embedded, formalin fixed neurological tissues. The critical constraint on this method is the size of the template target bearing the simple sequence repeat, which should ideally be less than 165 base pairs.

Acute femoral neuropathy after renal transplantation is an uncommon and rarely recognized complication. Recovery of the nerve is usual. Although rare, five cases have come to our attention in the past twenty years. A detailed clinical and electrophysiological analysis with a six month follow-up is presented. A review of sixteen other reported cases is also provided. The possible pathophysiology including direct compression and nerve ischemia, is discussed. We believe that nerve ischemia, possibly caused by a steal phenomenon, occurs in all cases following the anastomosis of the graft renal artery to the internal iliac artery, with a superimposed component of compression in some cases. The severity of ischemia probably determines the degree of recovery.