Intraoperative monitoring during surgery for acoustic neuroma: benefits of an extratympanic intrameatal electrode.

OBJECTIVES: To assess the utility of an extratympanic intrameatal electrode for intraoperative monitoring during acoustic neuroma and other cerebellopontine angle tumour surgery and to define the neurophysiological and surgical factors which influence hearing preservation. METHODS: Twenty two patients, 18 with acoustic neuromas and four with other cerebellopontine angle tumours, underwent intraoperative monitoring during tumour excision. The extratympanic intrameatal electrode (IME) was used to record the electrocochleogram (ECoG) and surface electrodes to record the brainstem auditory evoked response (ABR). RESULTS: The compound action potential (CAP) of the ECoG was two and a half times greater in amplitude than wave I of the ABR and was easily monitored. Virtually instant information was available as minimal averaging was required. Continuous monitoring was possible from the commencement of anaesthesia to skin closure. The IME was easy to place, non-invasive, and did not interfere with the operative field. Operative procedures which affected CAP or wave V latency or amplitude were drilling around the internal auditory meatus, tumour dissection, nerve section, and brainstem and cerebellar retraction. Hearing was achieved in 59% of patients. CONCLUSIONS: The IME had significant benefits in comparison with other methods of monitoring. The technique provided information beneficial to preservation of hearing.

Autonomic function in a cohort of children with diabetes.

129 diabetic children in Avon County participated in a longitudinal study of the evolution of microvascular disease together with 129 age- and sex-matched controls. Diabetic children had mean (+/- SD) age 12.7 (+/- 3.4) years (range: 3.7-16.8), mean (+/- SD) diabetes duration 3.9 (+/- 3.2) years (range: 0.1-13.4) and mean (+/- SD) HbA1 11.1% (+/- 2.2) (range: 6.5-18.2). Cardiovascular autonomic function was studied by four heart rate (HR) tests using a computerized system of HR monitoring. As a group, diabetic children had higher mean HR (p = 0.0004) and reduced max/min HR ratio while standing (p = 0.001), compared with the control children. HR ratio while standing was the only variable related to diabetes duration (r = -0.20, p = 0.018), while no correlation of HR variables with glycaemic control was found. Twenty diabetic children (15.5%) had one abnormal HR test. Ten diabetic children (7.7%) demonstrated abnormality in two or more HR tests. When compared with the other diabetic children in the cohort, these ten children were found to be younger in age (mean age: 9.4 vs 12.0 yr, p = 0.05), but did not otherwise differ in terms of diabetes duration or glycaemic control. No pubertal or sex effect in the development of diabetic autonomic neuropathy was detected. These findings suggest that autonomic function may be impaired early in childhood diabetes, independent of the duration of the disease or the quality of glycaemic control.

Functional outcome in patients after excision of extracanalicular acoustic neuromas using the suboccipital approach.

An audit of surgery for acoustic neuroma was carried out to determine the frequency and nature of postoperative symptoms and their impact upon the patient's quality of life and vocation. Fifty-six patients were interviewed between 6 months and 5 years (mean 26 months) after surgical excision of an acoustic neuroma. The objective surgical results in these patients are good, with normal or near normal functional preservation rates of 80% for the facial nerve (House-Brackmann grade I/II), and 27.3% for a previously functioning acoustic nerve. Despite this there was no significant overall reduction in the reported occurrence of balance problems, tinnitus, headache and other neurological sequelae of the tumour after surgical excision. In 20% of the patients persistent symptoms, including deafness and facial weakness, had prevented the resumption of former social activities. As a result of these symptoms 8.6% of the patients were certified medically unfit for work, but of those employed preoperatively over 70% had returned to their jobs. The success of neuro-otological surgical management of acoustic neuroma is offset by some degree of chronic morbidity. Our patients expressed the need to know whether their symptoms would resolve, but were often too afraid to ask. Patients can be reassured that the majority resume their former social and vocational activities, but should be advised that some symptoms can persist or occur de novo after surgery. Our data suggest that early intervention would reduce the incidence of these troublesome sequelae.

Pupil size in diabetes.

Sympathetic function was studied in 101 diabetic children and 102 age and sex matched control children, as part of a longitudinal study of the evolution of microvascular disease in the population of diabetic children and adolescents in Avon County. The median (range) age of the diabetic population was 13.5 (6.0-17.2) years, the duration of diabetes was 4.0 (0.4-13.9) years, and glycated haemoglobin (HbA1) was 10.9 (7.0-18.1)%. Pupillary adaptation in darkness, as an index of sympathetic neuropathy, was measured using a Polaroid portable pupillometer. Diabetic children had a significantly smaller median pupillary diameter, measured as the pupil/iris ratio and expressed as a percentage, than control children (median (range) 62.9 (50.3-72.1) v 65.9 (52.2-73.8)). Pupillary diameter was significantly related to diabetes duration (r = -0.22), HbA1 (r = -0.34), systolic blood pressure (r = -0.25), diastolic blood pressure (r = -0.49), and mean albumin/creatinine ratio on random urine samples (r = -0.26). Pupillary diameter was not related to age (r = -0.1). Eight (7.9%) diabetic and four (3.9%) control children were identified as having abnormal pupillary dilation in darkness. In comparison with the rest of the diabetic population, these diabetic children had longer diabetes duration and poorer glycaemic control. Polaroid pupillometry has demonstrated subclinical autonomic neuropathy in a population of diabetic children and adolescents. These abnormalities were related to poor metabolic control, long diabetes duration, and also to other indices of microvascular disease.

Development of visual evoked potentials following intrauterine growth retardation.

Visual evoked potentials to flash (FVEP) were recorded in 23 symmetrically growth retarded newborns of between 32 and 39 weeks gestational age and 41 normally grown controls. At 9 months post term FVEP recordings were repeated in 14 of the growth retarded and 26 of the control infants. The development of two long latency negative components of the wave form of the neonatal FVEP was delayed in the growth retarded infants. The amplitude of a long latency negative peak in the 9 month post term FVEP was reduced in the growth retarded infants. We suggest that intrauterine growth retardation may affect the development of secondary activity in the visual cortex.

Abnormal development of visual function following intrauterine growth retardation.

Vernier acuity was measured at 40 weeks post term in 18 infants born with symmetric intrauterine growth retardation (IUGR) and 32 normal (N) infants. Grating acuity was also measured in 12 IUGR and 26 N infants. The mean vernier detection threshold (V.min) was 0.4 octaves higher in the IUGR than in the N infants (P less than 0.04). The mean grating detection threshold (S.min) was 0.2 octaves lower in the IUGR infants (NS). The mean ratio of S.min to V.min was significantly lower in the IUGR infants (1.5 IUGR, 2.7 N, P less than 0.05). V.min was significantly negatively correlated with the head circumference of the IUGR infants at 40 weeks post term. Vernier acuity depends on visual processing at a cortical level. The normal grating acuity in the IUGR infants implies that cortical, rather than optical or retinal factors, underlie the reduced vernier acuity (high V.min). We suggest that the cortical representation of visual space is affected by IUGR.

Cricothyroid muscle paralysis: its recognition and diagnosis.

Cricothyroid muscle paralysis is often missed as the symptoms are not dramatic and the laryngeal observations, on conventional indirect mirror examination, are inconclusive. The anatomy and physiology of the superior laryngeal nerve (SLN) and cricothyroid muscle are described. Three case reports are presented to illustrate our diagnostic techniques. Videofibrolaryngoscopy and electromyography are found to be invaluable tools for the diagnosis of this condition. The importance in diagnosing this entity is discussed.

Nerve conduction studies.

Nerve conduction studies provide unique quantitative information about neurological function in patients with a variety of neuromuscular disorders. This article emphasizes the need for careful selection of the appropriate procedures, informed interpretation of the data, and correlation of the results with the clinical information about each individual patient's problem, in order to obtain the maximum possible value from the investigation.

Aldose reductase inhibition in diabetic neuropathy: clinical and neurophysiological studies of one year's treatment with sorbinil.

In a double-blind placebo-controlled trial the effect of Sorbinil (250 mg daily) on diabetic neuropathy was examined. After a 2-month run-in placebo period (with three major assessments) 21 patients were randomized to Sorbinil and 10 to placebo, and all were studied for a further 12 months with neurophysiological measurements at 3-month intervals of nerve conduction velocity in multiple nerves, autonomic function tests, vibration thresholds as well as clinical examination and an extensive self-assessment of symptoms. Two subjects on Sorbinil treatment developed a hypersensitivity reaction and were withdrawn. Metabolic control and severity of neuropathy was not significantly different between groups. There were no changes in symptoms as judged by self-assessment scores. No patient entered the trial with neuropathic ulcers but ulceration developed in 4 patients during Sorbinil treatment and in 1 of the placebo group. No beneficial effect of Sorbinil was demonstrated on either the clinical manifestation or on the neurophysiological measurements made in these neuropathic diabetic patients over 12 months of treatment.

Developmental wave form analysis of the neonatal flash evoked potential.

A multiple regression technique was used to describe the wave form of the flash evoked potential (VEP) in 64 neonates born between 28 and 39 weeks of gestation. The successive appearance of new features in the VEP with increasing gestational age at birth was used to define 5 components, of which specimens were obtained by averaging VEPs of 18 selected infants. The VEPs of the other 46 infants were expressed as linear sums of the components, each multiplied by a weighting coefficient. The method accounted for 74 +/- 11% (mean +/- 1 S.D.) of the rms power of the observed VEPs and was used to demonstrate significant effects on wave form maturation from fetal growth retardation and maternal smoking in pregnancy.

Clinical and neurophysiological studies with the aldose reductase inhibitor, sorbinil, in symptomatic diabetic neuropathy.

The effect of sorbinil (200 mg daily for 4 weeks) was examined in 13 patients, mean age 59.7 years (range 42-72 years), with symptomatic diabetic neuropathy of mean duration 6 year (range 1-18 years). In this double-blind, placebo-controlled crossover trial, studies were made of motor, sensory and autonomic nerve function, severity of painful symptoms and duration of sleep. One patient was withdrawn because of an adverse reaction to sorbinil. In the other 12, constant mean values for glycosylated haemoglobin A1 between 11% and 12% indicated stable though not ideal diabetic control throughout the study. Example values for nerve conduction velocity on placebo and active treatment were: 44.3 +/- 5.9 and 44.8 +/- 5.1 metres/s (mean +/- SD) for median motor nerve, 38.4 +/- 8.2 and 37.2 +/- 7.7 metres/s for median sensory nerve. Thus there was no significant effect of sorbinil on conduction velocity in these or any other of the motor and sensory nerves tested. Abnormal autonomic function was not improved by sorbinil. Subjective pain scores on a 10 cm visual analogue scale were 4.2 +/- 2.4 on placebo and 4.3 +/- 2.4 after sorbinil. Duration of sleep on placebo and active treatment was 6.1 +/- 1.6 and 6.2 +/- 1.7 h/night, respectively. We were not able to detect any beneficial effect of sorbinil on painful diabetic neuropathy in our patients.

Treatment of hepatic encephalopathy with metronidazole.

Neomycin, an antibiotic which is primarily active against the aerobic gut flora and hence reduces the endogenous production of ammonia, is a well-recognised form of treatment for acute or acute on chronic hepatic encephalopathy. This study suggests that metronidazole may be a useful alternative or even adjunctive treatment for such patients. Theoretical and practical justifications for the use of this drug are presented. The results of a week's prescription of each drug have been assessed by changes in clinical and biochemical criteria, including electroencephalograms and arterial ammonia sample. In the treatment of a series of 11 mildly or moderately, and seven severely affected, patients with histologically confirmed cirrhosis, metronidazole is shown to be as effective as neomycin.

Ataxia--its causes, measurement, and management.

This paper reviews the various types of ataxia, and some related clinical manifestations. Methods of measuring normal and abnormal movement are then discussed, followed by a consideration of management and specific and symptomatic treatments.

Intravenous administration of diazepam in patients with chronic liver disease.

The EEG response and drug kinetics after intravenous infusion of diazepam at 1-0 mg/min until nystagmus, dysarthria, and moderate sedation developed, has been investigated in five normal subjects and 17 patients with chronic liver disease. Diazepam induced adequate premedication with a similar clinical response in all subjects with no adverse reactions. Maximal response was during or within five minutes of infusion. The dose of diazepam required in liver chronic disease was 17-9 +/- 1-4 mg (M +/- SEM) compared with 27 +/- 5-4 mg in controls (p less than 0-01). Dose correlated significantly with serum albumin (p less than 0-05). Baseline mean dominant frequency (MDF) and slow wave index (SWI) significantly correlated with albumin (p less than 0-01). After diazepam, the MDF decreased and SWI increased. The change was greatest at the time of maximal clinical response. It was greater in liverdisease and was greatest in patients with previous hepaticencephalopathy. In spite of reduced dose requirements in liver disease, there was no significant difference in plasma concentration at the end of drug infusion...

Intention tremor--a method of measurement.

A method of measuring and analysing intention tremor using a linear accelerometer is described. Reasons are given for measuring this particular parameter of the tremor, for using this specific energy conversion device, and for employing the particular form of analysis. A comparison of the numerical values obtained for the amount of tremor activity, compared with a corresponding clinical grading, is made for 30 patients with intention tremor due to a variety of pathological causes. It is shown that the method gives clear correlation with the clinical assessments, although certain discrepancies are noted, and their importance discussed.