NHL Journal of Medical Sciences/July 2014/Vol 3/Issue 2 18

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1 Research article NIHSS Score: A handy tool to predict vascular occlusion in acute ischemic stroke Ronak Shah*, Chintal Vyas**, Jyoti Vora*** *Senior Resident, **Assistant Professor, ***Associate Professor, Dept of Medicine Smt NHL Municipal Medical College, Ahmedabad Abstract Background and objectives In ischemic stroke therapies like thrombolytic and mechanical recanalisation can dramatically improve clinical outcome. So in initial hours from clinical examination we can select those patients who are candidates for such therapies. National Institute of Health Stroke Scale (NIHSS) Score is such handy tool to predict stroke outcome. Several studies report that a higher NIHSS score was associated with more severe vascular lesions in patients with acute stroke. Here our aim is to evaluate the acute ischemic stroke according to NIHSS Score and to evaluate the relationship of NIHSS score and MR Angiographic findings in patients who were examined within the first hours after stroke onset. Methods In this prospective study, fifty patients with clinical features of acute stroke syndrome and showing ischemic stroke on CT scan brain were enrolled over the period of 2 years. NIHSS Score was calculated in all of them. All patients were undergone Magnetic Resonance Angiography (MRA) of brain. Depending on MR Angiographic findings patients were divided in different groups. Results Time interval from stroke onset to presentation was min while from stroke onset to MR imaging was min. The mean NIHSS Score in our study is Out of fifty patients, 29(58%) patients had visible arterial occlusion on MR Angiography (MRA) while 21(42%) had not. NIHSS Score was higher in Central occlusion group (internal carotid artery, main stem of middle cerebral artery and basilar artery) than Distal occlusion group (main branch of middle cerebral artery, anterior cerebral artery and posterior cerebral artery) (P value <0.0001). At NIHSS Score > 10, positive predictive value to detect arterial occlusion on MRA was around 89%. With an NIHSS Score > 12, positive predictive value to find a central occlusion on MRA was 87%. At NIHSS Score 10, sensitivity and specificity for detecting visible arterial occlusion was 86%. Conclusion: There is significant correlation between NIHSS Score and the presence and location of vessel occlusion. At the NIHSS Score 10 sensitivity, specificity and positive predictive value for presence of arterial occlusion on MR Angiography are optimal. Key words: NIHSS Score, MR Angiography, ischemic stroke Introduction Cerebrovascular diseases is one of the three leading cause of death in world along with cancer and heart disease. The average incident of stroke is about 2:1000 population. Risk of stroke increases with age such that after fifth decade the incidence doubles with each decade of life. Developing countries like India have been also burdened with cerebrovascular diseases. 1 Stroke is an emergency condition. In ischemic stroke therapies like thrombolytic and mechanical recanalisation can dramatically improve clinical outcome. So in initial hours from clinical examination we can select those patients who are candidates for such therapies. National Institute of Health Stroke Scale (NIHSS) Score is one such handy tool to predict stroke outcome. Specifically, it has been used in thrombolysis trials to include or exclude patients from active treatment. 2,3,4 Several studies examined relationships between initial NIHSS score and vascular imaging techniques report that a higher NIHSS score was associated with more severe vascular lesions in patients with acute stroke. 5 Although cerebral arterial imaging is necessary, this scoring system helps physicians to make decisions regarding early management in acute ischemic stroke especially in developing countries like India where imaging facilities are scarce in remote places. So here our aim is to evaluate the acute ischemic stroke according to National Institute of Health Stroke Scale (NIHSS) Score and to evaluate the relationship of NIHSS score and MR Angiographic findings in patients who were examined within the first hours after stroke onset. Methods Patients admitted in emergency ward and general ward of our institution with clinical features of acute stroke syndrome were screened in this prospective study over a period of twenty four months. Each patient received assessment for the following aspects. 1. Careful history paying special attention to demographic patient data, vascular risk factors (hypertension, diabetes, ischemic heart disease, valvular heart disease etc), intervals from symptom onset to admission. 2. Detailed clinical and neurological examination. 3. Non contrast CT brain performed to rule out intracranial haemorrhage. NHL Journal of Medical Sciences/July 2014/Vol 3/Issue 2 18

2 Table 1 Clinical data of stroke patients studied Cases 50 Sex n (%) Male 32 (64%) Female 18 (36%) Median age (years ) 59 Mean age Risk factors n (%) Diabetes mellitus 16 (32%) Hypertension 32 (64%) Smoking 24 (48%) Dyslipidemia 17 (34%) Ischemic heart disease/stroke 07 (14%) Time interval (min) mean with SD and range Stroke onset to presentation Stroke onset to MR imaging Criteria for selection: 1. Patients with clinical features of acute stroke syndrome admitted in our institute within 12 hours of onset. 2. Patients with ischemic stroke after CT scan brain. Patients with intra cranial haemorrhage and patients having transient ischemic attacks were excluded. Fifty patients fulfilling above criteria were enrolled in this study. In all enrolled patients neurological assessment was carried out using NIHSS Score with eleven different clinical variables. NIHSS Score was calculated in all fifty patients. All patients were undergone Magnetic Resonance Angiography (MRA) of brain within few hours of presentation. After MRA patients were divided in to two major groups, one with visible arterial occlusion on MRA and another without visible arterial occlusion. Patients with visible arterial occlusion on MRA were further subdivided into six groups according to their vessel occlusion site. 1. Internal carotid artery (ICA) group 2.main stem of middle cerebral artery (MCA M 1 ) group 3. Main branch of MCA (M 2 ) group 4. Anterior cerebral artery (ACA) group 5. Posterior cerebral artery (PCA) group 6. Basilar artery (BA) group. Out of them occlusion in Basilar, ICA and MCA-M 1 is considered as a central occlusion while rest are distal occlusion. If a patient showed two or more occluded arteries, he was put in to larger artery group (e.g. if the ICA and the ipsilateral M 1 segment were occluded, the patient was allocated to the ICA group). By clinical findings and ischemic lesions seen on MRI patients were divided into a group with carotid territory (ICA, ACA and MCA) and another with vertebrobasilar territory (BA and PCA) strokes. Statistical analysis was performed with the SPSS 17.0 statistical software package (SPSS Inc). Results Table 1 reports main clinical findings from the study. In our study group 32(64%) patients were male and 18(36%) were female. Majority of patients belong to 6 th decade (n=38,76%). The most prevalent vascular risk factors in our study group were hypertension (n=32,64%) and smoking (n=24,48%). Time interval from stroke onset to presentation was min while from stroke onset to MR imaging was min. Table 2: Distributions of patients by NIHSS Score NIHSS Score Number Percentage (%) 00 to to to to More than In Table 2 distributions of patients by NIHSS Score depicted. As per Table II highest numbers of patients were seen in 6 to 10 NIHSS Score group. The mean NIHSS Score in our study is Out of fifty patients, 29(58%) patients had visible arterial occlusion on MR Angiography while 21(42%) had no visible arterial occlusion. Among patients with visible arterial occlusion, 16(55%) had central occlusion while 13(45%) had distal occlusion. Table 3 shows patient distribution according to MR Angiography findings and median NIHSS Score in each subgroup. Highest number of patients were with MCA-M 2 occlusion (n=12.41%) as per Table 3. There were no patients with posterior cerebral artery occlusion. Median NIHSS was highest (32) in the Basilar Artery group and lowest (6) in the no occlusion group. Table 3: Patient distribution according to MR Angiography findings and mean NIHSS Score. Central occlusion Distal occlusion Basilar ICA MCA-M 1 MCA-M 2 ACA PCA Number Percentage Median NIHSS Score NHL Journal of Medical Sciences/July 2014/Vol 3/Issue 2 19

3 Table 4: Demographic data of different groups Group Central Distal P value No P value occlusion occlusion occlusion Number of patients Age median (range) (yr) 68 (38-85) 55 (48-80) (38-85) 0.18 Sex (Male) 8 (50%) 12 (92%) (57%) 0.39 Hypertension 12 (75%) 8 (61%) (57%) 0.39 Diabetes mellitus 7 (43.8%) 4 (30.8%) (23.8%) 0.29 Dyslipidemia 8 (50%) 4 (30.8%) (23.8%) 0.19 Smoking 6 (38%) 11 (85%) (33%) 0.07 IHD/Stroke/Valvular heart 2 (12.5%) 2 (15.4%) (14.3%) 0.9 disease Interval from stroke onset to presentation mean SD (min) Interval from stroke onset to MR angiography Mean SD (min) Demographic data of each group are shown in Table 4. Smoking was observed most frequently in the distal occlusion group (P 0.01). No other significant differences in baseline characteristics were observed. Figure I shows number of patients with visible arterial occlusion in specific NIHSS group. Figure shows correlation between NIHSS Score and chances of visible arterial occlusion on MR Angiography. In group with NIHSS Score 0-5, only one patient (11%) had visible arterial occlusion out of nine. While in group with NIHSS Score above 20, all patients (100%) had visible arterial occlusion on MR Angiography. So increase in NIHSS Score was associated with more chances of visible arterial occlusion which is graphically demonstrated in Figure I. Figure II shows NIHSS Score with range and median in different subgroups of stroke patients studied. As per Figure comparison of Occlusion and No Occlusion group is done by NIHSS Score. Median NIHSS Score is higher in occlusion group 16 than in No occlusion group 6 which is statistically significant (p < ). Same way patients with visible arterial occlusion, divided in to Central and Distal occlusion groups, were also compared by NIHSS Score. Patients with Central occlusion had higher median NIHSS Score 20 compare to Distal occlusion group 11 (p<0.0001). Figure III shows probability for detecting arterial occlusion on MR Angiography at a single value of NIHSS Score. It is evaluated with logistic regression method. There is clear association between NIHSS Score and its predictive probability to detect visible occlusion on MR Angiography. NHL Journal of Medical Sciences/July 2014/Vol 3/Issue 2 20

4 regression method. There is clear association between NIHSS Score and its predictive probability to detect visible occlusion on MR Angiography. Discussion National Institute of Health Score Scale (NIHSS), developed by National Institute of Health, is a fifteen item neurologic examination stroke scale used to evaluate the effect of acute cerebral infarctionn on level of consciousness, language, neglect, visual field loss, extraocular movement, motor strength, ataxia, dysarthria and sensory loss. NIHSS Score is widely used to assess the severity of acute ischemic stroke and to evaluate effectiveness of clinical therapy on stroke recovery. It has been used in many trials and is validated tool to predict stroke outcome. 6,7 The examination requires less than ten minutes to complete and is superior to simpler clinical stroke scales. It can be used by non-neurologists and nurses and patients can be scaled retrospectively from chart records. 8,9 Several studies, examined relationships between baseline NIHSS score and vascular imaging techniques such as ultrasonography, CT angiography and MR angiography, show high NIHSS Score associated with significant vascular occlusion. 10,11 In our study, out of 29 patients having NIHSS Score 10, 25 patients (86%) showed visible arterial occlusion on MR Angiography. Lewandowski et al 4 studied patients with stroke within 3 hr of stroke onset in the Emergency Management of Stroke bridging trial by using angiography. In that study, 17 (77.3%) of 22 patients with NIHSS scores 10 displayed occludedd arteries in the carotid system. This minor difference may be due to the differing interval between stroke onset and vascular imaging and due to the methods that evaluate occlusive lesions. Sensitivity and specificity of NIHSS Score for detecting visible arterial occlusion in MR Angiography is depicted as a graphical presentation in Figure IV. As noticed from the graph Sensitivity and specificity line crossess at the level of NIHSS Score of 10 at which sensitivity and specificity is near 86%. So at NIHSSS Score 10 sensitivity and specificity is optimum. Similar results were achieved by Mokotoo and Urs Fischer. 12,13 At NIHSS Score > 10, positive predictive value to detect arterial occlusion on MRA is around 89%. With an NIHSS Score > 12, positive predictive value to find a central occlusion on MRA was 87%. In study by Urs Fischer at NIHSS Score > 10, positive predictive value to detect arterial occlusion on MRA is around 96% while an NIHSSS Score > 12, positive predictive value to find a central occlusion on MRA was 91% %. In the present study, 4 (13.7%) of 29 patients with NIHSS scores 10 displayedd no arterial occlusion. This can be due to spontaneous reopening of the occluded artery immediately before MR Angiography. No significant differences were observed between NIHSS Scores of patients with left- and right-sided stroke in our study. In our study mean NIHSS Score in right sided stroke is and on left sided stroke is Similar results were found by Makoto et al. There were studies showing that patients with right-sided stroke may have a low NIHSS score despite substantial DWI lesion volume. 14 We have not measured DWI lesion volume in our patients that is limitation of our study. The potential value of baseline NIHSS Score in identifying those stroke patients who are likely to progress has been established. 15 Some recent studies performed in stroke patients showed the significant association of vessel occlusion and perfusion weighed imagingg (PWI) Diffusion weighed imaging (DWI) mismatch, which is considered as the ischemic tissue at risk that can potentially be salvaged. Though NIHSS Score does not substitute for vascular imaging, the results of present study will help the clinician to select such patients. The present study displayed some limitations. Though we have performed clinical examination immediately after admission, due to MRI availability and economical constrains, the mean time from stroke onset to MRA is 11 hours. This can underestimate cerebral arterial occlusion in our study. Conclusion There is significant correlation between NIHSS Score and the presence and location of vessel occlusion. At the NIHSS Score 10 sensitivity, specificity and positive predictive value for presence of arterial occlusion on MR Angiography were optimal. In our country due to economical constraints and limited facility for imaging studies, it is difficult to select stroke patients for thrombolytic therapy in window period. NIHSS Score do not replace vascular imaging but help to select such patients in initial hours. NHL Journal of Medical Sciences/July 2014/Vol 3/Issue 2 21

5 Acknowledgments We acknowledge Mr Hemant Tiwari for helping us in statistical analysis of our study. We are also thankful to Dr Pratik Patel for his help. References 1. Epidemiology of non-communicable diseases: Stroke. Park s Textbook of PSM, 19 th Edition. 2. Clark WM, Wissman S, Albers GW, Jhamandas JH, Madden KP,Hamilton S; ATLANTIS Study Investigators. Recombinant tissue-type plasminogen activator (alteplase) for ischemic stroke 3 to 5 hours after symptom onset: the ATLANTIS study: a randomized controlled trial. J Am Med. Assoc. 1999;282: Furlan A, Higashida R, Wechsler L, Gent M, Rowley H, Kase C, Pessin M, Ahuja A, Callahan F, Clark WM, Silver F, Rivera F; PROACT Investigators. Intra-arterial prourokinase for ischemic stroke: the PROACT II study: a randomized controlled trial.j Am Med Assoc. 1999;282: Lewandowski CA, Frankel M, Tomsick TA, Broderick J, Frey J, Clark W, Starkman S, Grotta J, Spilker J, Khoury J, Brott T. Combined intra-venous and intra-arterial r-tpa versus intra-arterial therapy of acute is-chemic stroke. Emergency Management of Stroke (EMS) Bridging Trial. Stroke ; 30: Derex L, Nighoghossian N, Hermier M, Adeleine P, Froment JC, Trouillas P.Early detection of cerebral artery occlusion on magnetic resonance angiography: predictive value of the baseline NIHSS score and impact on neurological outcome.cerebrovasc Dis 2002;13: Muir KW, Weir CJ, Murray GD, Povey C, Lees KR. Comparison of neurological scales and scoring systems for acute stroke prognosis. Stroke. 1996;27: Adams HP Jr, Davis PH, Leira EC, Chang K- C, Bendixen BH, Clarke WR, Woolson RF, HansenMD. Baseline NIH Stroke Scale score strongly predicts outcome after stroke: a report of the Trial of Org in Acute Stroke Treatment (TOAST).Neurology. 1999;53: Kasner SE, Chalela JA, Lucaino JM, Cucchiara BL, Raps EC, McGarvey ML, Conroy MB, Localio AR. Reliability and validity of estimating the NIH stroke scale from medical records.stroke. 1999; 30: Williams LS, Yilmaz EY, Lopez-Yunez AM. Retrospective assessment of initial stroke severity with the NIH Stroke Scale. Stroke. 2000;31: Koga M, Kimura K, Minematsu K, Yamaguchi T. Ultrasono-graphic prediction of patients outcome in hyperacute ischemic stroke.eur J Ultrasound2002;15: Verro P, Tanenbaum LN, Borden NM, Sen S, Eshkar N. CT angiography in acute ischemic stroke: preliminary results.stroke 2002;33: Urs Fischer, MD; Marcel Arnold, MD; Krassen Nedeltchev, MD; Caspar Brekenfeld, MD;Pietro Ballinari, MSc; Luca Remonda, MD; Gerhard Schroth, MD; Heinrich P. Mattle, MD. NIHSS Score and Arteriographic Findings in Acute Ischemic Stroke Makoto Nakajima, Kazumi Kimura, Toshiyasu Ogata, Tatsuro Takada, Makoto Uchino, and Kazuo Minematsu Relationships between Angiographic Findings and National Institutes of Health Stroke Scale Score in Cases of Hyperacute Carotid Ischemic Stroke AJNR Am J Neuroradiol25: , February Fink JN, Selim MH, Kumar S, et al. The association of National Institutes of Health Stroke Scale scores and acute magnetic resonance imaging stroke volume equal for patients with right- and left-hemisphere ischemic stroke? Stroke 2002;33: DeGraba TJ, Hallenbeck JM, Pettigrew KD, Dutka AJ, Kelly BJ. Progression in acute stroke: value of the initial NIH stroke scale score on patient stratification in future trials. Stroke 1999;30: NHL Journal of Medical Sciences/July 2014/Vol 3/Issue 2 22