Objective  To describe a 38-year-old woman with known Klippel-Feil syndrome who developed lateropulsion.

Results  The results of magnetic resonance imaging were consistent with rubrothalamic stroke. The cerebral angiogram confirmed vertebral artery dissection at the level of her previously observed bony abnormality.

Conclusions  Hypermobility adjacent to fused vertebrae subjects the vertebral artery to increased shear forces. Thus, Klippel-Feil syndrome may be a predisposing factor for vertebral artery dissection. Moreover, to our knowledge, this case represents the second known case of rubral lateropulsion.

We describe a patient with 2 rare occurrences that are causally related: lateropulsion due to rubrothalamic stroke in the context of vertebral artery dissection associated with Klippel-Feil syndrome.

REPORT OF A CASE

One year later, she woke up with unsteadiness and a strong tendency to fall to the right. A neurologic examination revealed severe lateral sway to the right (lateropulsion), hypometric vertical saccades, gaze-evoked horizontal/torsional nystagmus accompanied by oscillopsia, and mild left-sided lower facial droop. Brain magnetic resonance imaging revealed an 8-mm acute infarct involving the left paramedian thalamus and the red nucleus (Figure 1), along with an old left cerebellar infarct. A cerebral angiogram showed left vertebral artery dissection at C2-C3 (Figure 2). The patient received aspirin, 325 mg daily. The lateropulsion and facial weakness resolved within the next week. She remained free of any new neurologic deficit over the next year.

View larger version (59K): [in this window] [in a new window] Figure 1. A, Coronal view of a T2-weighted magnetic resonance image shows hyperintensity in the left red nucleus and paramedian thalamus. The small arrows indicate the area of the infarct; the large arrow, the contralateral red nucleus. B, The key is given for the anatomical structures. C indicates caudate nucleus; CM, centromedian nucleus; DM, dorsomedial nucleus; LP, lateral posterior nucleus; N, substantia nigra; R, red nucleus; S, subthalamic nucleus; and VPM, ventroposteromedial nucleus.9

View larger version (43K): [in this window] [in a new window] Figure 2. Left vertebral artery dissection with (A) and without (B) superimposed shadow of the vertebral bodies. The large arrow indicates flame-shaped tapering and the string sign; the small arrow, a muscular branch.

COMMENT

Neurologic complications in patients with Klippel-Feil syndrome are infrequent and mainly reported in children.^2-6 In the older literature,³ deficits were attributed to mechanical compression of the brainstem without any investigation of the vertebral arteries. A vascular cause has been discussed in the literature⁶ more recently: angiographically proven compromise of vertebral arterial blood flow on extension and rotation of the head in children with Klippel-Feil syndrome has been demonstrated. In addition to compromising blood flow, hypermobility predisposes the arterial wall to shear forces during movement, causing intimal damage or dissection as a source of thromboembolism.¹⁰ Case reports^{2, 4-6} exist of children with Klippel-Feil syndrome presenting with apnea, loss of consciousness, or posterior circulation strokes secondary to vertebral artery dissection. To our knowledge, only one case of dissection in adults has been reported.⁷ Therefore, we surmise that persisting shear forces from hypermobile vertebrae adjacent to fused segments caused the vertebral artery dissection in our patient, leading to thromboembolic stroke.

The cardinal symptom in our patient was lateropulsion, the tendency to fall laterally due to an acute unilateral vestibular system dysfunction in the context of normal motor function, sensation, and coordination.¹¹ It is observed ipsilateral to lesions of the labyrinth, vestibular nerve, vestibular nuclei, and pontomedullary areas and contralateral to pontomesencephalic and thalamic lesions.^{8, 11-12} There are case reports^13-15 of ipsilateral and contralateral cerebellar lesions causing lateropulsion as well. Our patient's magnetic resonance image showed a lesion in the red nucleus and paramedian thalamus. To our knowledge, only one previous case report⁸ of rubral lateropulsion existed: the researchers postulated that the lesion in the red nucleus interrupted the ascending fibers of the crossed dentatorubrothalamic tract, causing "rubral" gait disequilibrium without tremor, ataxia, sensory loss, or weakness. Thalamic lateropulsion, also known as thalamic astasia, is usually due to a lesion in the ventrolateral thalamic area.^{12, 16} Anatomical studies support this finding: vestibulothalamic, dentatorubrothalamic, and fastigiothalamic fibers join the thalamic fascicle adjacent to the red nucleus and end in the ventrolateral area of the thalamus (ventroposterolateral and ventrolateral).^16-17 Accordingly, to our knowledge, no reports exist of paramedian thalamic lesions causing disequilibrium.¹⁸ Therefore, we believe it unlikely that the paramedian thalamic lesion caused the lateropulsion in our patient. We postulate that the lesion in the red nucleus area interrupted any of the vestibulothalamic, dentatorubrothalamic, or fastigiothalamic fibers or the thalamic fascicle, providing further evidence that a lesion in the area of the red nucleus can cause lateropulsion.

Multiple researchers^19-20 have already recommended flexion-extension cervical spine radiography in the examination of children presenting with vertebral artery dissection because of the many observed coexisting vertebrobasilar anomalies in such children. Because only 50% of individuals with Klippel-Feil syndrome have the classic triad of low posterior hairline, short neck, and limited cervical motion, this condition can easily escape detection.¹ This could theoretically lead to cases of dissection without known antecedent trauma or neck hyperextension being erroneously categorized as spontaneous. Therefore, the combination of Klippel-Feil syndrome and vertebral artery dissection may well be underreported in adults.

In conclusion, this case broadens the differential diagnosis of posterior circulation ischemic stroke, especially in young adults. We, therefore, consider it reasonable to obtain cervical spine imaging in unexplained adult cases as well. Finally, lateropulsion occurring in isolation may be secondary to a central lesion, such as in the area of the red nucleus, thus warranting neuroimaging for further examination.

From the Department of Neurology, University of Iowa Hospitals and Clinics, Iowa City.

REFERENCES