Since Galvani discovered electric current in a nerve/muscle preparation of a frog’s leg in the late eighteenth centry, great strides have been made in the study of the role of electricity in nerve/muscle physiology. It was not until 1948 however, that elect ical stimulation of the nerve was put into clinical use (1). Thereafter, nerve conduction studies (NCV), and electomyography (EMG) have become standard procedures in the diagnosis of neuro-muscular disorder. In Sierra Leone, these facilities became available in 1982 with the setting up of a Neurological service at Connaught Hospital, the main referring hospital in Sierra Leone. Unlike other electrophysiological procedures such as electrocardiography (ECG) and electroencephalography (EEG) that could he competently performed and interpreted by trained technicians, or even by computer, the performance of NCV and EMG is still firmly rooted in the domain of the neurologist or neuro-physiologist. In a developing country such as Sierra Leone, manpower limitations in these specialities may seriously affect the delivery of such services to me community. The present review often years ol neuroclectrodiagnostic procedures at Connaughl Hospital is an attempt to assess the proper utilization of these faclilities as diagnostic aids in the Sierra Leonean, the constraints encountered in their performance, and to consider ways of improving the efficiency ol the service.
Complete records ol all cases ol NCV and EMG done from 1982 to 1992 were available for review. This was made possible by a comprehensive record system containing Oic relevcant clinical, demographic and eleclro-physiological data ot all patients investigated during this time. Excluded were incomplete data due to various reasons, such as electrical failure during examinations, electrode malfunction and patients’ non-cooperation. Patients ages ranged from six months to eighty five years with a mean of 41 years. The sex ratio was 1.4 females to one male. Investigations were mainly of two types; 1. nerve conduction studies which included measuring the velocities of nerve conduction (NCV) in both sensory and motor nerves, as well as latencies and amplitudes. This investigation was used in diagnosing peripheral nerve disorders like peripheral neuropathies, mononeuropathies, root and plexus abnormalities, as well when repetitive stimulation was also done. 2 electomyography which is the study of muscle fibres by needle electrodes and was the main diagnostic procedure in myopathies, muscular dystrophies and muscular atrophies. Both these procedures were done on a two channel electromyograph machine (Neuropack men - 3102, Nihon-Koden, Japan) according to standard methods (2), in an air-conditioned room at fairly constant temperature, lack of averaging equipment reduced the accuracy and sensitivity of measuring very small sensory potentials. Cases were referred from all specialties i.e internal medicene, surgery, obstertics and gyneacology, paediatrics as well as from general practitioners. All investigations were done by a neurologist (DRL), assisted by a nurse. A cost revovery fee was levied on most patients, excepting those case where non-affordability was a consideration.
During the period under review, 642 new patients were investigated. Some patients had serial examination but only the initial evaluation was considered for the purpose of this study. The commonest indication for testing was mononeuropathy accounting for 38% of all cases. Root and plexus abnormalities. and peripheral neuropathy accounted for 22% and 20% respectively. Other indications included traumatic nerve injury, myopathies, and myasthenia gravis.
Table 1 : Clinical indications for clectrodiagnosis
|% of total|
|Root and plexus lesions||22|
|Subjective Unilateral Sensory symptoms||3.7|
|Traumatic nerve lesions||2.3|
|Burning feet syndrome||2.2|
Three Further Categories of patients presenting with unilateral subjective sensory symptoms but no clinical signs, affecting upper and lower limbs, 2. those with burning feet. and 3. a miscellaneous group including patients with tremor, dystonia, dyskinesia, and ataxia.
Table 2 : Details of three commonest indications for NCV and EMG
|1. PRERIPHERAL NEUROPATHY|
|3. ROOT AND PLEXUS|
|a. cervical / brachial||53|
(Table 2) shows details of the tree commonest categories referred for investigation. Median nerve lesions specially the carpal tunnel syndrome, were by far reprted (3,4). This \as folloed by facial and ulnar nerve lesions. Cervical root and brachial plexus lesions were slightly more prevalent than lumbar root lesions. In the peripheral neuropathies, the mixed sensori-motor type was present in 65% of cases, while pure sensory neuropathy accounted for 19% and motor neuropathy 16%. This distribution is similar to that noted in Nigeria (5). The Motor neuropathy included motor neurone disease and the Gullian-Barre syndrome, the latter accounting for the majority of cases.
In order to assess the usefulness of electrodiagnosis in confirming clinical diagnosis, or in establishing a diagnosis, an attempt has been made to calculate the percentage of cases examined in which the investigation contributed to the establishment of a diagnosis (Table 3).
Table 3: Usefulness of MCV and EMG in diagnosis of neuroniuscular disorders of neuromuscular disorders
|% of cases in which EMG and MCV aided clinical diagnoses|
|ROOT AND PLEXUS|
|Subjective unilateral sensory symptoms||0|
|Burning feet syndrome||0|
This showed that the procedures were of significant diagnostic value in the following conditions; peripheral neuropathy, mononeuropathies, traumatic nerve injury, myopathies, and myasthenia gravis. They were of some value in root and plexus injuries and of virtually no use in subjective hemisensory symptoms, burning feet syndrome, and all the movement disorders. In the case of peripheral neuropathy, pure sensory neuropathies were less commonly diagnosed, but classification of neuropathies into axonal and demyelinating types by NCV contributed to the differential diagnosis of underlying causes.
Replacing electrodes particularly concentric needle electrodes were the most expensive recurring costs of operations. Other consumable items included electrode gel, ground (earthing) leads, stimulator pads and recording heat sensitive paper. With frequent voltage fluctuations, equipment failure was not uncommon. Assuming that 500 patients paid an average ofLe 3000 ($6) per examination during the study period, the total of $3000 was barely enough to cover these costs. It should also be pointed out that the equipment is now thirteen years old and virtually at the end of its lifespan and that a current replacement cost is in the region of$ 50,000.
In pursuing the objectives of the Alma-Ata declaration to provide health for all by the year 2000, great emphasis has been placed on primary health care (PHC). It is becoming clear however that tertiary care cannot be ignored and should be developed to a level capable of supporting and augmenting PHC programmes. This requires the provision of diagnostic and therapeutic facilities in various specialties. In a review of neurological problems in Sierra Leone, neuromuscular diseases accounted for about 15% of all cases seen (6), while in Nigeria over 10% of neurological cases were attributed to neuromuscular conditions (7). Moreover up to 40% of the neuropathies in Nigeria were related to nutritional abnormalities (7), an important PHC considerations. NCV and EMG are considered essential in the investigation of these cases. The cost profile of the procedure clearly shows that affordable cost recovery is inadequate to sustain the service, hence budgetary provisions must be made to maintain and replace equipments as required. In general, these costs must be offset against large sums spent on individuals for treatment overseas for conditions for which local expertise is available but specialized units poorly equipped. Some of this money should be used to equip our tertiary centres. Perhaps the major factor limiting the use of the facility is the shortage of skilled manpower. With only one neurologist in practice, the equipment is underutilized. This is.supported by the number of new patients seen during the study period, averaging less than seventy a year. Tests are usually suspended, sometimes for long periods, during his absence. Training of non-specialized medical officers in performing some of the basic investigations is conceivable eventhough a sound knowledge of neurology is essential. This is only possible if medical officers are allowed to spend a longer time at their posts. Under the present circumstances, efficiency can still be enhanced if optimum use is made of both time and equipment. In this regard, proper selection of cases referred is essential. Patients with movement disorders, burning feet or subjective hemisensory symptoms do not benefit from electrodiagnosis, while those with clinical evidence of peripheral neuropathy, mononeuropathy and myopathy gain the most. Referring physicians should know the indications, usefulness and limitations of NCV and EMG, or otherwise seek neurological opinion before requesting investigations. In conclusion, electrodiagnosis is an essential aid in the investigation of neuromuscular disoeders in Sierra Leoneans. This service cannot however be sustained by affordable cost recovery and requires financial support from the public health sector for its maintenance and development. Proper selection of cases and training of non-specialized medical personnel will enhance the delivery and efficiency of the service.