H. van Crevel

Lumbar puncture and the risk of herniation: when should we first perform CT?

Abstract Death following lumbar puncture (LP) is feared by physicians. Many opinions are found in literature on the question whether computed cranial tomography (CT) should be performed before LP, to prevent herniation. These opinions are mainly based on retrospective studies and pathophysiological reasoning.In this review the difficulties in the decision whether we should perform CT before LP are discussed. It is explained that the concept of “raised intracranial pressure” is confusing, and that the less ambiguous terms “brain shift” and “raised CSF pressure” should be used instead. Brain shift is a contraindication to LP, whether CSF pressure is raised or not, and whether papilloedema is present or not. Subsequently, recommendations are offered for indications to perform CT before LP, grouped according to the safety and clinical utility of LP.

Reversible dementia : more than 10 % or less than 1 % : a quantitative review

Dementia is reversible in some cases and these should be diagnosed without over-investigating the many others with irreversible disease. To estimate how often dementia can be reversed, we carried out a quantitative review of studies reported between 1972 and 1994 in which reversible dementia was diagnosed and outcome after treatment was assessed. We found 16 studies comprising 1551 patients. The percentages of reversed dementia varied widely: from 0 to 23% for partial and from 0 to 10% for full reversal. Depression and drug intoxication were the most frequent causes of reversible dementia, followed by metabolic and neurosurgical disorders. The percentage of both partial and full reversal of dementia has fallen in recent years, to less than 1% for both in the four most recent studies. This decrease could be associated with the change from an inpatient to an outpatient setting and the use of stricter diagnostic methods. We conclude that reversible dementia is very rare in an outpatient setting when using strict diagnostic methods. This has important implications for the diagnostic strategy in patients with dementia: major procedures should be performed selectively. In patients with clinical characteristics of Alzheimers disease, CT of the brain is unlikely to detect a treatable cause of dementia.

Reversible dementia in elderly patients referred to a memory clinic.

Abstract Dementia has a reversible cause in some cases, and these should be diagnosed without over-investigating the many patients with irreversible disease. We prospectively studied the prevalence of reversible dementia in a memory clinic, determined the added value of investigations compared with clinical examination and assessed the outcome of treatment of potentially reversible causes by measuring (1) cognition, (2) disability in daily functioning, (3) behavioural changes and (4) caregiver burden. Two hundred patients aged 65 years and over were examined, using the CAMDEX-N. If they were demented, the probable cause was diagnosed clinically and confirmed or excluded by a standard set of investigations, which were done in all patients. Of the patients, 170 (mean age 79.2 years) were demented; 31 were treated for potentially reversible causes. At follow-up after 6 months, no patients showed complete reversal of dementia. Five patients improved on clinical impression, but only one on clinicial measurement. Thirty patients were cognitively impaired, but not demented; seven were treated. Judged clinically, three patients improved, but on assessment only one did so; she recovered completely. Blood tests often produced diagnostic results that were not expected clinically, but electroencephalography and computed tomography of the brain did not. None of the investigations had an effect on outcome of dementia after treatment. We conclude that in elderly patients referred to a memory clinic, the prevalence of reversible dementia is of the order of 1%, if outcome after treatment is assessed by a standardized measurement. We recommend blood tests in all patients, to detect not only metabolic causes of dementia but also co-morbidity possibly worsening the dementia. Other investigations can be performed on clinical indication. Clinical evaluation remains the mainstay of diagnosis in dementia.

Reliability of the clinical and electromyographic examination of tendon reflexes

SummaryThe reliability of clinical examination of the tendon reflexes was examined by studying inter-observer agreement. Twenty patients were examined by three neurologists. The briskness of the tendon reflexes in arms and legs was scored on a nine-point scale. In 28% of the 160 examined reflexes the observations disagreed 2 scale units or more. Disagreement on the presence of asymmetry occurred in 45% of the 80 reflex pairs. In 15% one observer judged a reflex pair to be symmetrical while another observer found asymmetry of at least 2 scale units. In a second experiment clinical observation of apparently asymmetrical quadriceps reflexes was compared with measurement by surface electromyography. A significant, semi-logarithmic relationship was found between clinical scores and measured reflex amplitudes. Measured reflex asymmetry always agreed with clinical asymmetry, and the magnitudes of right-left amplitude differences were correlated with the magnitude of clinically observed asymmetry. The bedside examination of tendon reflexes is subject to considerable inter-observer disagreement.

Measurement of tendon reflexes by surface electromyography in normal subjects.

SummaryA simple method for measuring the tendon reflexes was developed. A manually operated, electronic reflex hammer was applied that enabled measurement of the strength of tendon taps. Reflex responses were recorded by surface electromyography. Stimulus-response relations and latencies of tendon reflexes in the biceps, triceps, quadriceps and triceps surae were examined in 40 healthy subjects. A characteristic relation between stimulus strength and response amplitude was found which could be described by an empirical function. Latencies of both arm and leg reflexes were linearly related to the height of the subjects. Variations of reflex amplitudes within and between subjects were comparable with previous results obtained with more complicated techniques. Although repeatability of measurement of the amplitude is limited by the variability of reflexes, significant agreement was found between repeated measurements. Most reflex amplitudes were diminished during repeated examination after a short interval. Both measurement and clinical examination showed the frequent occurrence of left-right asymmetry of reflex amplitudes. These left-right differences were reproducible to a significant degree on repeated measurements after more than 2 years.

Early diagnosis of dementia: which tests are indicated? What are their costs?

Abstract Dementia is reversible in a minority of patients, and these should be diagnosed but without subjecting the majority with irreversible disease to an excessive set of investigations. Should a battery of ancillary investigations be performed routinely in dementia? Or can these tests be carried out as clinically indicated? Three arguments are important to answer this question. (a) Reversible dementia is rare: about 1% of cases. (b) If the clinical criteria for diagnosing primary degenerative disease are used consistently, the results of investigations can be predicted with sufficient accuracy, except those of blood tests. (c) Treatment of reversible dementia has the best results in its most frequent causes: depression and drug intoxication; however, treatment of medical and surgical causes of dementia may also be effective. Based on these three considerations, we propose the following guideline in the setting of a memory clinic: to perform blood tests in every patient with dementia, but also to perform other tests, such as electroencephalography (EEG) and computed tomography (CT), as clinically indicated.