Prévost sign in acute ischemic stroke: A diagnostic clue

A 76-year-old male presented with a sudden loss of consciousness, reduced verbal response, and left-sided weakness. On arrival at the emergency department, he was within the thrombolysis window period, with a National Institutes of Health Stroke Scale (NIHSS) score of 12. Neurological examination revealed left-sided hemiplegia and signs consistent with hemispatial neglect, including difficulty responding to left-sided stimuli and a rightward bias in spatial attention.

Non-contrast computed tomography (CT) of the brain demonstrated hypodensity with loss of grey-white matter differentiation and sulcal effacement in the right temporoparietal lobe, consistent with an acute ischemic infarct (Figure 1a). Additionally, linear hyperdensity within the right Sylvian fissure raised suspicion for thrombosis in the M2–M3 segments of the right middle cerebral artery (MCA). Deviation of both eyes towards the right was noted, consistent with Prévost sign (Figure 1b).

Magnetic resonance imaging (MRI) with magnetic resonance angiography (MRA) confirmed an early hyperacute non-haemorrhagic infarct in the right temporoparietal lobes and corona radiata and non-visualisation of the right inferior MCA (M2, M3, and M4 segments) (Figures 2a, 2b and 2c). Early thrombolysis with intravenous tenecteplase was initiated, resulting in rapid clinical improvement.

A follow-up CT scan showed no haemorrhagic transformation, and the patient was ambulatory at discharge (Figure 3).

Background

Prévost sign, characterised by conjugate gaze deviation towards the side of the lesion, is a clinically significant indicator of hemispheric stroke [1]. This sign reflects disruption of the frontal eye field on the affected side, resulting in unopposed contralateral eye field activity. Recognition of the Prévost sign is essential for the rapid localisation of cerebral pathology and diagnosis of large-vessel occlusion.

Clinical Perspective

The early identification of the Prévost sign plays a critical role in diagnosing acute ischemic stroke and guiding immediate clinical decisions [2]. This sign correlates with large-vessel occlusion and serves as a predictor of stroke severity and outcome [3]. In resource-limited settings where access to advanced imaging is restricted, clinical signs such as the Prévost can effectively guide early management decisions.

Imaging Perspective

Imaging findings play a complementary role in confirming the diagnosis suggested by clinical signs [4]. In this case, the non-contrast CT scan revealed subtle hypodensity in the temporoparietal region and a hyperdense Sylvian fissure sign, suggesting a thrombus in the MCA. This finding prompted the initiation of thrombolysis. Although no direct frontal or parietal lobe involvement was seen on imaging, the gaze deviation and hemispatial neglect observed clinically suggest a functional disruption in the right parietal lobe and its associated attention networks [6]. The MRI with MRA confirmed the extent of the infarct and ruled out haemorrhagic transformation, thus validating the clinical decision. The observed gaze deviation toward the lesion, combined with hemispatial neglect and other clinical signs, highlights the significance of these findings in stroke localisation.

Outcome

The patient exhibited significant neurological improvement following thrombolysis. At the time of discharge, the patient was ambulatory with improved motor function, and follow-up imaging confirmed the absence of haemorrhagic transformation. The NIHSS score reduced from 12 to 4, reflecting the success of early intervention. This case highlights the importance of rapid thrombolysis for improving functional recovery in acute stroke management. Recognition of the Prévost sign led to prompt administration of thrombolysis, resulting in significant neurological improvement without complications. Studies have shown that early thrombolysis or thrombectomy improves outcomes in large-vessel strokes, with the Prévost sign serving as a key indicator for timely intervention [5].

Teaching Points

• Diagnostic value of the Prévost sign: Recognising conjugate gaze deviation toward the side of the lesion aids in the early identification of large-vessel occlusions.
• Prognostic significance: The Prévost sign correlates with stroke severity and guides therapeutic decisions, such as thrombolysis or thrombectomy.
• Clinical and imaging integration: Combining clinical signs with imaging optimises the diagnosis and management.
• Use in resource-limited settings: The Prévost sign is particularly valuable in settings where advanced imaging may not be immediately available.
• Impact of early intervention: Timely thrombolysis improves recovery and minimises complications in acute stroke management.

Written informed consent was obtained from the patient for publication.