Multiple sclerosis : experience in neuroimaging era from western India.
31 patients of multiple sclerosis (MS) diagnosed in the last six years in a large teaching hospital were reviewed. The hospital incidence of 0.85% of total admissions in neurology unit in western India is comparable to the series from other parts of India. The mean age at onset was slightly lower compared to other series. The female preponderence was noted in addition to higher incidence of Devic's syndrome. Visual loss (47%) and motor weakness (27%) were the commonest presenting symptoms. The clinical pattern was more similar to Asian series of MS than the western series. All patients underwent magnetic resonance imaging (MRI) scan. 24 out of 25 MRI of Brain and 15 out of 16 MRI of spine were abnormal. CSF immuno-globulins were raised in 80% of patients who underwent CSF study. The data has been compared with other Indian, Asian and Western series.
The worldwide distribution of multiple sclerosis continues to attract a great deal of attention and has been the subject of exhaustive reviews. The hope, which has encouraged these studies, has been that a distinctive pattern would emerge which could provide a clue to the aetiological factor for the disease. The methods employed include population surveys and analysis of hospital records of patients diagnosed to have multiple sclerosis. Accurate population based surveys are hampered by three factors : i) the low prevalence of the disease ii) the long time interval between the first symptom and the establishment of the diagnosis and, iii) the lack of a single diagnostic test for the establishment of the diagnosis and the impractibality of using autopsy data for diagnostic validity due to the extended life expectancy of most patients.
The lack of centralised medical infrastructure makes population studies especially difficult in our country. All studies in India, so far, are based on hospital experience at major medical centers. This study documents the six-year experience of a major medical centre in western India.
Patients admitted to the Neurology service at King Edward VII Memorial Hospital, Mumbai, between January 1991 and December 1996 constituted the subjects for this clinical study. Well known Poser's criteria for the diagnosis of multiple sclerosis was strictly adhered to. Other causes for multiple lesions and/or events were actively sought and excluded in appropriate cases. Devic's disease was diagnosed when patients showed bilateral visual impairment with tranverse spinal cord lesion concomitantly or within a short interval of a month.
Laboratory investigations included CSF examination for total immunoglobulin, neuroimaging (MRI or CT scan) and evoked potentials (VEP, SSEP, BAER). Autoimmune profile and biochemical tests were performed in individual cases. Patients were classified as clinically definite (CD), laboratory supported definite (LSD), clinically probable (CP) or laboratory supported probable (LSP) based on Poser's criteria.
3639 patients were admitted to the Neurology unit of our hospital during the 6 year period from January 1991 to December 1996. 31 of these patients were diagnosed to have MS, which constituted 0.85% of the total admissions.
The study group consisted of 31 patients. According to Poser's criteria, 22 patients (70%) had `clinically definite', 5 (17%) `clinically probable' and 4(13%) `laboratory supported probable' multiple sclerosis. There were 3 cases of neuromyelitis optica (Devic's syndrome) constituting 10% of the group. There were 10 male and 21 female patients in the group. The Male:Female ratio was 1:2.1. The youngest patient was 9 years old and the oldest was 47 years old at the time of onset of symptoms. The mean age of onset was 25.3 years. The average age at onset was lower in females (21.8 years) than in males (28.8 years). [Table I]
The commonest initial symptom was visual loss, which ccurred in 14 patients (47%). Weakness was the next common presenting symptom in 8 patients (27%). Diplopia occurred in 5 patients (16%). Seizures were the first symptom in 3 patients and were recurrent throughout the course in two of them. Ataxia was the presenting symptom in 4 patients (13%).
Loss of vision was the commonest sign, seen in 24 patients (7%). Visual loss was unilateral in 11 and bilateral in 13 patients. Motor weakness was the next common sign, seen in 22 patients (71%)-4 had hemiparesis, 7 had quadriparesis and 12 had paraparesis. 52% of cases complained of sensory loss. 42% and 39% patients had bladder involvement and ataxia respectively. One patient had tonic seizures and four (13%) had emotional lability. Internuclear ophthalmoplegia was seen in one patient and positive Lhermitte's sign in two cases (Table II and III). Details of various sites of lesion is given in Table III.
CSF examination was done in 28 patients and 20 of the samples were tested for IgG. CSF IgG was elevated in 16 (80%) cases. Magnetic resonance imaging (MRI) was done in all cases. 25 patients underwent MRI of brain. White matter hyperintensities on T2W images suggestive of MS were present in 24 of the patients (96%). MRI of thoracic spine was abnormal in all the six cases where it was done. Nine of the ten cervical spines MRIs (90%) were abnormal. The yield of evoked potentials was much lower than MRI. SSEPs showed the highest sensitivity (85%, cases studied 7) followed by VEP (60%, cases done 15) and BAER (16%, cases studied 6). Number of cases studied were however small.
Studies by Kurtzke et al, Acheson, Sutherland et al have confirmed the Limburg hypothesis that the frequency of multiple sclerosis increases with distance of the surveyed area from the equator. It is also generally accepted that the incidence of multiple sclerosis is low throughout Asia and Africa, irrespective of latitude.
The hospital incidence of MS in our centre is 0.85 percent. While this figure does not reflect the regional incidence of the disease, it compares well with the figures reported from other hospital based studies over the country--0.85% reported from Delhi and 0.05% reported from south India.
The preponderance of women in our series is consistent with that seen in western literature and in the Japanese series. This was contrary to other Indian series, which reported a preponderance of male patients.,,, Visual impairment (77%) was the most common symptom during the course of the illness in our series; its incidence was similar to that reported in the Japanese (74%) and the Asian (70%) series and much higher than that reported by Bhatia et al (34%) or US Army series (34%).
Motor weakness was almost as common as visual loss and the frequency was similar to the Japanese and US series. Ataxia was much less frequent than in the Asian patients and the series from Delhi. Though sensory loss as the initial complaint was rare, it was a fairly frequent demonstrable sign during the course of the illness (52%). Sphincter involvement in our patients was comparable to the Japanese, Asian and the Indian studies, and was much higher than the rate reported in the US army series. [Table II]
Seizures occurred in 3 patients and were the presenting symptoms in all three of them. Tonic painful spasms were reported by one patient only. The US series did not report any tonic spasms. Devic's syndrome was seen in 3 of the 31 cases (10%) and was comparable to the rates reported in other Asian series (7%) but much higher than the Delhi series.
Magnetic resonance imaging has now become one of the key investigations in the diagnosis of multiple sclerosis. It is reported to be positive in a varying percentage of cases in different studies, the figures ranging from 50% to 95%., In our study, the Brain MRI showed lesions consistent with MS in 96% of cases. The true accuracy of MR imaging remains difficult to determine but the overall yield is reported to be 80%. The high sensitivity of MRI is offset by its lack of specificity; though certain characteristics may strongly favour MS, none of them are diagnostic by themselves.
Evoked potentials are useful to identify clinically silent lesions in the visual, somatosensory pathways or the brainstem. The incidence of abnormalities on VEPs in various studies range from 75-97%. SSEPs have been reported to be abnormal in 50%-70% and BAERs from 20-50% of cases. In our series, 60% of VEPs and 16% of BAERs were abnormal, but the tests were performed in a few cases only. Recently, some studies have compared the yield of MRIs to evoked potential testing in the diagnosis of multiple sclerosis but the results are varied. Some have found the former to be superior, others have found evoked potentials to be more sensitive. Yet others have found MRI to be equivalent to CT with trimodal evoked potential testing and conclude that it is the first test (EPS or MRI) that provides the majority of the discriminatory power to the clinician. A survey of the general practices of clinicians in the evaluation of MS has revealed that most clinicians choose MR imaging prior to evoked potential testing. The basis for comparing a structural test like an MRI to a physiological test like EPs has been criticized.
The CSF IgG was detected in 80% of the 20 patients in whom the test was performed. The Asian series reported raised CSF protein in 49% of the cases but did not report presence of CSF IgG. Verma et al found elevated CSF IgG in two of the four cases in which it was estimated.
In conclusion, the incidence rate in western region of the country is comparable to the recent hospital series in north India. The mean age at onset was slightly lower compared to the other series, and there was a greater preponderance of women, as has been seen the world over. The clinical pattern is more similar to the Japanese and Asian series than the western series. While internuclear ophthalmoplegia was rare, the incidence of Devic's syndrome was found to be higher than that reported in other Indian series.