Wernekinck commissure syndrome: An illustrative case with review of various etiologies

INTRODUCTION

Wernekinck commissure syndrome (WCS) is an exceptionally rare brainstem syndrome disorder characterized by bilateral cerebellar ataxia, variable eye movement dysfunction, and infrequent delayed-onset palatal myoclonus or tremor. Worldwide, WCS comprises 0.6–2.3% of midbrain ischemic stroke syndromes.^[1] In an Indian study, approximately 18.6% of patients with pure midbrain infarctions were found to have signs and symptoms consistent with WCS.^[2] Neurologic deficits seen in WCS are believed to be caused by disruptions of the superior cerebellar peduncles, medial longitudinal fasciculi, and the central tegmental tract. It follows paramedian strokes in the caudal midbrain at the level of the inferior colliculus. Given the limited number of published cases and the potential for under-recognition due to its subtle clinical and radiological features, we present a detailed case of a 60-year-old hypertensive, chronic smoker male who developed sudden-onset gait and limb ataxia, dysarthria, and diplopia, ultimately diagnosed as WCS. We further supplement this case with a focused literature review to better characterize common clinical patterns, imaging findings, etiologies, and outcomes associated with this rare syndrome.

ILLUSTRATIVE CASE

A 60-year-old chronic smoker, hypertensive male presented to the causality with a hyperacute onset gait ataxia and four-limb ataxia for 1 day, which started while the patient was sitting in his chair. When he tried to get up from the chair, he was swaying to the sides, and his family members explained the pattern of walking as if he were drunk. He walked with feet wide apart and sustained fall due to imbalance as well. The patient also describes that he had tremors in both his hands whenever he tried to pick up a glass of water while sitting and even had spillage of food on holding a spoon while eating. The tremors were not present at rest or during sleep. He had a complaint of change in speech in the form that attendants noticed it was slurred, and he started speaking with syllables separately and slowly with intermittent pauses. The patient also complained of double vision. He claimed that on looking toward the sides, he used to see two images of an object or person, one clear and one blurred, but denied shaking of the image. There was no impairment in his memory, history of loss of consciousness, loss of smell, color vision loss, or visual blurring or loss, facial numbness, difficulty chewing or making food bolus, facial asymmetry, tinnitus, aural fullness, hearing loss, vertigo, or drooping of the shoulder. He could move both his arms and legs, but the movements were clumsy. Patient denied any occurrence of trauma or any episodes of dizziness, nausea, or vertigo before or during onset of the symptoms. The patient denied regular intake of any drug or any substance of abuse other than alcohol. No history of similar condition was found in other family members.

On examination, the patient was fully conscious and alert with clear orientation toward time, place and person as well surrounding environment. There was no neck stiffness. Cranial nerve examination revealed horizontal gaze-evoked nystagmus in both eyes and internuclear ophthalmoplegia in both eyes. The rest of the cranial nerve examination was unremarkable. Tone was normal in both the upper and lower extremities. Muscle power was Medical Research Council (MRC) grade 5/5 in upper and lower extremities. Deep tendon reflexes were MRC grade 1. Rectal tone was normal, and no urinary incontinence was noted. There were no sensory deficits. Cerebellar function assessment revealed impaired alternating repeated movements (dysdiadochokinesis), gait ataxia, intention and action tremors, impaired finger-nose testing, and heel-shin testing. His Modified Rankin scale (mRS) and National Institutes of Health Stroke Scale (NIHSS) were 4 and 5, respectively.

The patient was admitted for further evaluation to the inpatient unit. The routine investigations were done. Electrocardiography was suggestive of a rate of 80 beats/ min, sinus rhythm, normal axis with R waves in V5 and V6 and deep S waves in V1 and V2 suggestive of left ventricular hypertrophy (as per Sokolov Lyon criteria). A 2-D Echo scan was performed, which was suggestive of concentric left ventricular hypertrophy with normal ejection fraction. Laboratory results showed no signs of infection or inflammatory disease. His lipid profile showed deranged total cholesterol (280 mg/dL) and hypertriglyceridemia (350 mg/dL). Erythrocyte sedimentation rate, high-sensitivity C-reactive protein, antinuclear antibody by immunofluorescence assay, cytoplasmic antineutrophil cytoplasmic antibodies, perinuclear antineutrophil cytoplasmic antibodies, and serum homocysteine levels were within normal range. Computed tomography angiography could not be performed as the patient denied the investigation. His magnetic resonance imaging (MRI) Brain findings [Figure 1] demonstrated an area of diffusion restriction in the paramedian midbrain at Wernekinck Commissure with low apparent diffusion coefficient signal, confirming a paramedian infarct in the caudal midbrain consistent with WCS. Magnetic resonance angiography was not done due to refusal by the attendants. The patient was managed with antiplatelets, statins, antihypertensives, and supportive neurorehabilitation. He was discharged from the hospital with mRS of 4 and NIHSS of 5. Three months of follow- up revealed mRS of 3 and NIHSS of 4.

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Figure 1:

Magnetic resonance imaging brain (a and b) showing T2 weighted and fluid attenuated inversion recovery sequences showing subtle hyperintense in paramedian midbrain region (red circle) (Wernekinck Commissure) (c) Diffusion restriction (red circle) and (d) Low apparent diffusion coefficient signal in same region (red circle).

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DISCUSSION

Anatomically, the decussation of superior cerebellar peduncles and central tegmental tract constitutes the horseshoe-shaped Wernekinck commissure that is named after German anatomist Friedrich Wernekinck.^[3] The term WCS was initially used by

Lhermitte to describe symptoms resulting from a lesion in the superior cerebellar peduncles’ decussation characterized by bilateral cerebellar symptoms linked in the form of gait, trunk and limb ataxia, dysarthria which is of cerebellar variety, and ocular signs. Affected medial longitudinal fasciculi are the source of eye movement impairment, presenting as internuclear ophthalmoplegia. Tremors and palatal myoclonus are also reported in this syndrome.^[3,4-10] In general, due to sparing of pyramidal tracts and other cranial nerve nuclei, the upper motor neuron signs and signs of other cranial nerve dysfunction are not seen. The findings in the present case are in coherence with the available literature.

The existing literature reported only a few cases of WCS. Majority of the cases reported have vascular etiology leading to infarction in the midbrain, leading to WCS. Other possible etiologies include midbrain hemorrhage, demyelinating pseudotumor, optic neuromyelitis spectrum disease, and Hashimoto’s encephalopathy.^[4-10]

In the present case, midbrain infarction led to involvement of the Wernekinck Commissure, causing WCS. Analysis of seven eligible cases [Table 1] revealed several consistent trends. Most patients were in their fifth to seventh decade of life, with a slight male predominance. The predominant etiology was ischemic infarction of the caudal midbrain due to posterior circulation stroke. Clinically, bilateral cerebellar ataxia and internuclear ophthalmoplegia were nearly universal features, while dysarthria and tremor were frequently reported. MRI findings commonly showed diffusion restriction at the level of the superior cerebellar peduncle decussation. Outcomes across cases were generally favorable with conservative management, including antiplatelets and rehabilitation, though functional recovery varied based on initial severity and etiology.

Management of WCS includes treatment of underlying etiologies. Antiplatelet drugs, statins, and other supportive measures in the form of active rehabilitation involving physiotherapy, gait training, and speech therapy are the mainstay of treatment when etiology is vascular in origin. Whereas, in case of inflammatory pathologies as seen with Hashiomoto’s encephalopathy, steroids and intravenous immunoglobulins are preferred treatment of choice. Our patient was started on dual antiplatelet treatment in the form of aspirin 150 mg and clopidogrel 75 mg along with atorvastatin 40 mg daily for 21 days, following which he was switched to aspirin 150 mg and atorvastatin 40 mg daily. He had improvement in mRS and NIHSS on follow-up. Outcome is generally good with a stable to improving course on follow-up as reported in the literature.^[4-10] Strengths of the study include the rare syndrome reported from the region, which is probably one of its kinds, along with a literature review. Only limitation of this case is being single case report. This case highlights several diagnostic challenges inherent in WCS. Due to its rarity and overlapping features with other cerebellar and brainstem syndromes, WCS is often underdiagnosed or misattributed, particularly in the absence of classical motor or sensory deficits. Moreover, the subtle nature of MRI findings at the level of the superior cerebellar peduncle decussation demands high clinical suspicion and careful radiological assessment. The presence of bilateral internuclear ophthalmoplegia with cerebellar ataxia, in the absence of corticospinal involvement, can provide important diagnostic clues. This literature review opens up discussions on WCS and its etiologies and presentations beyond infarction.

CONCLUSION

WCS, though exceptionally rare, should be considered in the differential diagnosis of bilateral cerebellar dysfunction with ocular motor signs. Early recognition and timely neuroimaging are key to initiating appropriate management and improving neurological outcomes.