OBJECTIVE ASSESSMENT OF MUSCLE STRENGTH IN CHROIIIC RELAPSING DYS I M M U N E POLYRAD I CULO N E U ROPAT HY

Richard E. Appleton Ann M. Sykanda

Chronic relapsing dysimmune poly- radiculoneuropathy (CRDP) is an inflammatory, demyelinating disorder of the peripheral nervous system at one end of the spectrum of the polyneuropathies which include the Guillain-Barre syndrome. Alternative terms that have been used for this disorder include chronic relapsing polyneuritis, chronic inflammatory polyradiculoneuropathy and steroid-responsive recurrent polyneuro- pathy. The aetiology of this disease is unclear. Clinically, CRDP is characterised by the slow onset (usually over several months) of a sensorimotor polyneuro- patliy, which then becomes relapsing- remitting and/or steadily progressive (Dyck and Arnason 1984). There should not be any associated systemic disease, nor prior history of exposure to heavy metals or toxins. Investigations typically reveal marked slowing of nerve con- duction velocities, elevated cerebrospinal fluid protein and a normal serum immunoglobulin electrophoresis.

Therapeutic measures, including corticosteroids, other immunosuppressive drugs and plasmapheresis, have been used successfully in both the treatment and prevention of the acute relapses which are the hallmark of this disease. However, the response to these measures is neither consistent nor predictable in a single

patient or in a group of patients with this condition (Austin 1958, Dalakas and Engel 1981, Gross and Thomas 1981, Dyck et al. 1982, Tindall and Rollins 1986).

As with other neuromuscular diseases, repeated testing of muscle function of patients with CRDP is necessary in order to monitor the progress of the disease, and to assess efficacy of treatment. Traditional methods of muscle testing grade muscles according to their ability to work against gravity, and against resistance, as in the scale of the British Medical Research Council (1943).

The purpose of this longitudinal study was to monitor the course of chronic recurrent polyneuropathy in two female adolescent patients, using myometry. The main objectives were to discover any obvious temporal pattern to the relapses or remissions, and to evaluate the efficacy of various methods of treatment.

Patients and method Patients The patients’ clinical profiles and results of neurological examinations and investi- gations are detailed in Tables I to 111.

PATIENT 1 This girl has been treated with corticosteroids alone (alternate day or high-dose pulse methyl-

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TABLE I Clinical profiles

Patient I Patient 2

Age at onset (yrs) 13.5 10.5 Age at first relapse (yrs) 14*,5 11.25 Number of relapses 13 62 Presenting symptoms Progressive Paraesthesiae

lower-limb and lower- weakness limb

weakness Respiratory symptoms No No Bladder/bowel symptoms No No Visual disturbance No No Preceding viral infection No No Exposure to toxins No No Birth, development Normal Normal Past medical history Negative Negative Family history Negative Negative

'13 relapses over a three-year-period; 'six relapses over a four-year period.

TABLE I1 Neurological examination at first presentation

Patient I Patient 2

Motor function Walking Walking unaided; unaided;

broad-based normal gait; unable gait; unable to hop or to run stand on tiptoes; unable

to write Sensation (all

modalities) Normal Normal Deep tendon reflexes Absent Absent Plantar responses Flexor Flexor Cranial-nerve

examination Normal Normal Blood pressure

(standing) 95/70 100/60

prednisolone), or with a combination of cortico- steroids, azathioprine and plasmapheresis. The clinical response to these various therapies has been neither consistent nor sustained, and the over-all course of her disease has been gradually progressive. Currently she is well, with minimal distal weakness, and is receiving daily azathioprine (150mg) and plasmapheresis (two exchanges) every three weeks.

PATIENT 2 This girl has been treated with corticosteroids (alternate day or high-dose pulse methyl- prednisolone), either singly or in combination with azathioprine, and/or plasmapheresis. The clinical response was similar, though not identical, to that of patient 1: the over-all course of the disease has been less progressive, and on one occasion she regained normal muscle function (following her first steroid course). Also, unlike patient 1, it appeared that some of her previous weakness was iatrogenic, as a marked improvement was noted when her oral

366 prednisone was discontinued. Currently she is

receiving a three-day course of pulsed high-dose intravenous methylprednisolone because of a further relapse.

Method There are a number of disadvantages in using the Medical Research Council scale for measuring changes in muscle strength. It tends to be subjective, the intervals between the grades are disproportionate, and the amount of resistance in grades 4 and 5 is not specified. Furthermore, the scale is not sensitive to small changes in force (Hosking et al. 1976, Edwards and Hyde 1977, Hyde et al. 1983).

Responding to the need for a small, hand-held instrument for measuring muscle strength, the Hammersmith Hospital in London, in conjunction with Penny and Giles Transducers Ltd., developed a myometer which became commercially available in 1982 (Hyde et al. 1983). The myometer is battery operated and consists of a pressure transducer which measures force in kilograms, displayed on a digital readout. The applicator head of the instrument is placed in position, usually near the end of a long bone, and the patient is instructed to push with maximal force against the head while the physiotherapist pushes in the opposite direction with enough force to overcome the patient's power. Thus the peak force applied by the examiner in resisting a muscle group (as opposed to an individual muscle) is measured; the range of measurement is from 0.1 to 30kg.

When positioning of the patient and placement of the measuring head are performed in a standardized manner, test- retest and inter-rater reliability has been found to be significantly good (Hyde et al. 1983). The myometer has been used to assess boys with muscular dystrophy and to monitor drug therapy for adult patients with collagen diseases (Hyde et al. 1983).

With each of our two patients, repeated measurements of the power of nine key muscle groups were performed over a one year period by a physiotherapist using the myometer, and of grip strength using the Jamar dynamometer. The same examiner undertook each myometer muscle test, and standardized methods were used. In each case the first value was recorded, since immediately repeated measurements

TABLE. 111 Results of investigations (at k s t presentation and at first relapse)

Patient I Initial Relapse

Patient 2 Initial Relapse

CSF: protein' glucose cell-count

Nerve conduction motor' sensory

Serum immunoglobulins Creatine phosphokinase Antinuclear antibodies Rheumatoid factor Viral antibody studies3 Pulmonary function tests

1.14 1.25 Normal Normal Normal Normal

20-24 15-20 Slowed Slowed

Normal Normal Negative Negative Negative Normal

2.0 0.52 Normal Normal Normal Normal

- 3635 - Slowed

Normal Normal Negative Negative Negative Normal

'Normal CSF protein level 0.15-0.358/1; 'normal nerve conduction value 50-70 m/s (nerves tested-median and peroneal); 'viruses studied (paired sera)-rubella, CMV, Ebstein-Barr, varicella-zoster, herpes simplex, measles.

would have been influenced by fatigue. It muscle strength values increased sharply. was not possible to control for the time of By the autumn of the year the course of day testing was done. An effort was made her disease appeared to change; two to ensure that myometer testing was done severe, abrupt, closely-spaced relapses before and after each course of treatment, occurred, which responded promptly to and regularly during the intervals between pulsed methylprednisolone. treatment. The flow chart for patient 1 provides

objective, visual evidence of the efficacy Results of two plasma exchanges (rather than Data were transferred onto graphs, which one) in controlling her disease, and of the indicate at a glance recent changes in cyclical nature of the relapses. It was muscle strength, as well as maintaining a possible to plan regular exchanges at the perspective of change over the preceding cell separator unit and to prevent the months. Figures 1 and 2 represent graphs more severe manifestations of disease by of six muscle groups (three upper- intervening before the decline in muscle extremity and three lower-extremity) for strength values was complete. Once this each patient. regime was established the patient

maintained her ability to ambulate, Discussion despite fluctuations in the disease. She Figures 1 and 2 demonstrate the different was able to plan her life around these characteristics of the two patients. Patient scheduled exchanges, and staff involved 1 improved significantly after each course in the treatment also benefited from this of plasmapheresis, followed by rapid advance planning. deterioration in muscle strength after The chart for patient 2 demonstrates three to five weeks. The most dramatic that plasmapheresis was not effective and improvement in muscle strength occurred that oral prednisone was not only after pulsed methylprednisolone therapy. unnecessary, but also might have However, this improvement was sustained contributed to her muscle weakness. for only 48 hours, following which there Conversely, the value of pulsed methyl- was a rapid decline i n muscle strength. On prednisolone was emphasised. the other hand, patient 2 demonstrated a The sensitivity of the myometer as a slow, gradual improvement during the clinical tool is shown by the fact that on first six months of the year, with changes several occasions the early stages of in muscle strength bearing little relapse could be detected in both patients relationship to treatment until oral before they reported subjective feelings of prednisone was discontinued, when weakness. During periods of remission it

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Myometry Muscle Function Studies Patient 2 OlI Oral Prednime 8 Plasmaphererir fl Pulsad Methyl Prdnisalane

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was possible to determine whether muscle power had returned to the level of earlier remissions, but not if it had returned to 'normal', since as yet there are no normative values for different muscle groups of children of various heights. Studies on a population of normal school- children are planned. Accepted for publication 16th July 1987.

Acknowledgements The authors express their appreciation to Drs. John 368

Crichton and Bernard de Jong for permission to report their patients.

Authors' Appointments *Richard E. Appleton, M.B., B.S., M.A.(Oxon), D.C.H., M.R.C.P.(UK), Clinical Fellow in Paediatric Neurology, Division of Paediatric Neurology, Department of Paediatrics, University of British Columbia, Vancouver, B.C. Ann M. Sykanda, B.S.R., M.A.(UBC), Senior Physiotherapist, British Columbia's Children's Hospital, Vancouver, B.C.

*Correspondence to first author at B.C. Children's Hospital, 4480 Oak Street, Vancouver, B.C. V6H 3v4.

SUMMARY Chronic, relapsing dysimmune polyradiculoneuropathy is an uncommon disease which occasionally affects children. The relapsing-remitting and/or progressive symptoms may be refractory to treatment. Regular, objective assessment of muscle strength, visually displayed, facilitates knowledge of the natural history of the disease and predicts response to treatment, and thus optimum planning for treatment. Myometry, discussed in this report, appears to be an objective and useful technique for this purpose, as illustrated in two teenage girls with this disease.

RI~SUME Appreciation objective de la force musculaire chez les patients atteints d’une polyradiculoneuropathie dysimmune chronique rkidivante La polyradiculoneuropathie dysimmune chronique recidivante est une affection rare qui affecte parfois les enfants. La suite des remissiondrechutes et/ou les symptomes progressifs peuvent resister au traitement. L’appreciation rtguliere objective de la force musculaire, traduite visuellement, facilite la connaissance de I’histoire naturelle de I’affection et pridit la reponse au traitement, favorisant un planning optimum de traitement. La myomktrie discutee dans cet article, apparait une technique objective et utile a ce but, bien illustree chez deux adolescentes atteintes de cette affection.

ZUSAMMENFASSUNG Objektive Beurteilung der Muskelkraft bei Patienten mit chronischer, rezidivierender, dysimmuner Polyradiculoneuropath ie Die chronische, rezidivierende, dysimmune Polyradiculoneuropathie ist eine seltene Erkrankung, die gelegentlich bei Kindern auftritt. Die rezidivierenden-remittierenden und/oder progressiven Symptome konnen Therapie-resistent sein. Die regelmaflige, objektive Uberprufung der Muskelkraft, visuell veranschaulicht, fordert die Kenntnis des normalen Verlaufs der Erkrankung und prognostiziert die Reaktion auf die Therapie und somit eine optimale Therapieplanung. Die Myometrie, die in diesem Bericht diskutiert wird, scheint fur diesen Zweck eine objektive und gute Methode zu sein, was an zwei Madchen mit dieser Erkrankung gezeigt werden konnte.

RESUME N Evaluacidn objetiva de la fuerza muscular de pacientes con poli-radiculo-neuropatia disinmune, crdnica, de repeticidn La poliradiculoneuropatia disinmune, cronica de repeticion es una enfermedad no corriente que ocasionalmente afecta a niflos. Los sintomas de recaida-remision y/o progresiva pueden ser refractarios a1 tratamiento. La evaluation objetiva y regular de la fuerza muscular, visualmente expuesta, facilita el conocimiento de la historia natural de la enfermedad y predice la respuesta a1 tratamiento y con ello la planificacion optima de la terapia. La miometria, que se discute en esta comunicacion muestra ser una tkcnica objetiva y util para la finalidad citada, tal como se ilustra en dos niflos de 10 a 20 aflos de edad que padecian esta enfermedad.

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