Neurology -- Correspondence for Simon et al., 60 (1) 135-137

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Correspondence published:

Reply to Letter to the Editor: JE Simon, SC Morgan, JHW Pexman and AM Buchan (1 August 2003)

CT assessment of conjugate eye deviation in acute stroke: Silvia Di Legge, Vadim Beletsky, Vivek Jain, and Vladimir Hachinski (1 August 2003)

Reply to Letter to the Editor 1 August 2003

JE Simon,
Foothills Hospital
Calgary Stroke Program 1403-29th Street NW Room 1162 Calgary Alberta T2N 2T9 Canada,
SC Morgan, JHW Pexman and AM Buchan
Send Correspondence to journal:
Re: Reply to Letter to the Editor

jessica.simon{at}calgaryhealthregion.ca JE Simon, et al.

We agree with Dr Di Legge et al. that right hemispheric stroke may be under-recognised, identified late and thus under-treated with thrombolytic agents. Among all patients treated with tPA at our institution to date 38.4% had symptoms attributable to the right hemispheric. Evidence from the pooled carotid endarterectomy trials of 6092 subjects suggests that once carotid territory disease is recognised the ratio of left to right approaches one, at 1.13 (95%CI 1.09-1.17). [1]
The reasons Di Legge et al. postulate for the low rate of thrombolysis for right hemispheric strokes are all plausible. Many stroke databases are unable to provide the evidence for these observations however because they lack detailed information about patients who do not receive thrombolysis, including the affected hemisphere and the decision behind withholding thrombolytic agents. For this reason we support the efforts of the registry of the Canadian Stroke Network in the attempt to capture prospective data on a broader stroke population and to develop strategies to identify more thrombolytic candidates. One simple method that may help earlier identification of right hemispheric ischemia, particularly when the symptoms or clinical signs are subtle or missed, is to use the presence of rightward CED on CT. [2] This clinical application of the “CT eye sign” is facilitated by the high frequency of CED in right hemispheric strokes, compared to left hemispheric strokes, due to asymmetry in attentional mechanisms. [3]
Finally we agree that in our sample the absence of correlation between CED or a lone abducting eye and NIHSS score may relate to the relative insensitivity of this scale to right hemispheric stroke severity. [4] Currently we are examining this issue in a larger ischemic stroke population and will look for a correlation between CED and NIHSS for each hemisphere independently, both at presentation and follow-up.
References:
1) Rothwell PM, Eliasziw M, Gutnikov SA, Fox AJ, Taylor DW, Mayberg MR, Warlow CP, Barnett HJ; Carotid Endarterectomy Trialists' Collaboration. Analysis of pooled data from the randomised controlled trials of endarterectomy for symptomatic carotid stenosis. Lancet. 2003;361:107-116.
2) Simon JE, Kennedy J, Pexman JH, Buchan AM. The eyes have it: conjugate eye deviation on CT scan aids in early detection of ischemic stroke. CMAJ. 2003;168:1446-1447.
3) Mesulam MM. A cortical network for directed attention and unilateral neglect. Ann Neurol 1981;10:309-325.
4) Fink JN, Selim MH, Kumar S, Silver B, Linfante I, Caplan LR, Schlaug G. Is 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;33:954-958.

CT assessment of conjugate eye deviation in acute stroke 1 August 2003

Silvia Di Legge,
Department of Clinical Neurological Sciences LHSC
Windermere Road London, Ontario N6A 5A5 Canada,
Vadim Beletsky, Vivek Jain, and Vladimir Hachinski
Send Correspondence to journal:
Re: CT assessment of conjugate eye deviation in acute stroke

sdilegge{at}uwo.ca Silvia Di Legge, et al.

Simon et al. [1] evaluated the frequency of CT-assessed conjugate eye deviation (CED) toward the affected hemisphere in a consecutive series of acute stroke patients treated with recombinant tissue plasminogen activator (rt-PA). CED was observed in 43% of patients and a further 33% had a lone abducting eye (LAE). In this study, CED and LAE properly lateralized the side of the affected hemisphere in 81% (29/36) of patients with right hemisphere strokes and in 59% (42/71) of patients with left hemisphere ones, with a right/left ratio of 1.4:1. In a previous study, the clinically-assessed CED correctly lateralized the affected hemisphere in 62% of patients with right hemisphere lesions and 38% with left hemisphere ones with a right/left ratio of 1.6:1 [2].
Of note, in the series of Simon et al [1], with a 92.1% (106/117) prevalence of anterior circulation strokes, only 33% (35/107) had a right hemisphere lesion. Interestingly, in our series of 175 patients with anterior circulation ischemic strokes treated consecutively with rt-PA we observed a similar low proportion (39%, n=68) of patients with right versus left lesions [3]. Patients with right hemisphere stroke are less likely to be treated with rt-PA due to many factors: i) the misconception that damage to the right hemisphere affects patients less severely than left ones; ii) inadequate knowledge, within the community, of the symptoms and signs of non-dominant hemisphere stroke, compared to the familiar language disturbance of the dominant one; iii) some patients with right hemisphere stroke may only show poverty of movements with the left limbs and decreased visual exploration toward the opposite side as part of the neglect, and a tendency to keep the eyes closed due to eyelid apraxia; iv) the lack of a standardized and sensitive tool for assessing and monitoring stroke severity in acute right hemisphere ischemic stroke. The low sensitivity of the National Institute of Health Stroke Scale (NIHSS) in assessing stroke severity in right hemisphere stroke has been demonstrated by perfusion-weighted MRI findings [4], and this may account for the absence of correlation between the presence of CED/LAE and the NIHSS observed by the authors.
Unawareness of illness affects recovery: nevertheless, there are no evidence-based data targeting and monitoring the neglect syndrome and its changes after thrombolysis. Hillis et al. [5] observed that the administration of the simple “line cancellation” test is highly sensitive in assessing hemispatial neglect in patients with acute non-dominant hemisphere stroke. The authors observed that an improvement in test performance correlated to brain reperfusion.
Therefore, the CT-assessed CED, in conjunction with other tests sensitive to non-dominant hemispheric function should be studied in larger series of acute stroke patients in order to optimize the timely identification and treatment of patients with right hemisphere strokes.
References:
1. Simon JE, Morgan SC, Pexman JH, Hill MD, Buchan AM. CT assessment of conjugate eye deviation in acute stroke. Neurology 2003;60:135-137.
2. Tijssen CC, Schulte BP, Leyten AC. Prognostic significance of conjugate eye deviation in stroke patients Stroke 1991;22:200-202.
3. Di Legge S, Beletsky V, Poncha F, Cotton L, Hachinski V. The impact of hemispheric lesion side on use of rt-PA in acute stroke treatment. Neurology 2003;60 (suppl 1):A266.
4. Fink JN, Selim MH, Kumar S, Silver B, Linfante I, Caplan LR, Schlaug G. Is 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;33:954-958.
5. Hillis AE, Barker PB, Ulatowski J, Beauchamp NJ, Wityk RJ. A simple test of hemispatial neglect reflects change in tissue perfusion with intervention in acute nondominant hemisphere stroke. Stroke 2003, 34: 252.