Eight-and-a-half syndrome combined with an ipsilateral vertical gaze palsy: A pathophysiological explanation

A Rare Neuro-Ophthalmological Condition in a Patient with Lung Adenocarcinoma: The Eight-and-a-Half Syndrome, Case Report and Review of the Literature

The eight-and-a-half syndrome is a rare neuro-ophthalmological condition caused by a structural lesion in the dorsal portion of the pons, involving critical areas of the brainstem, i.e., medial longitudinal fasciculus (MLF), abducens nucleus, facial genu, and colliculus. It is characterized by internuclear ophthalmoplegia with horizontal gaze palsy and peripheral facial palsy. Although the syndrome is most frequently caused by vascular or demyelinating diseases, several different underlying causes might occur. Herein, we describe a case of the eight-and-a-half syndrome caused by a lung adenocarcinoma metastasis localized in the lower pontine tegmentum. Then, we review the current literature on the underlying causes of the eight-and-a-half syndrome.

Eight-and-a-half syndrome: a rare potentially life-threatening disease

Purpose: To report a case of eight-and-a-half syndrome presenting with a conjugate horizontal gaze palsy, an ipsilateral internuclear ophthalmoplegia, and an ipsilateral lower motor neuron-like facial palsy.

Methods: A 56-year-old male who came in for limitation of extraocular muscle motion – wherein the only remaining movement is abduction of the left eye – and right-sided facial weakness. Magnetic resonance imaging revealed a well-defined lesion resembling a cavernoma, at the level of the ponto-medullary junction.

Results: Eight-and-a-half syndrome results from a lesion affecting the paramedian pontine reticular formation, the median longitudinal fasciculus, and the facial nerve fascicle on one side. In this case, a cavernoma at the level of the ponto-medullary junction was compressing the important pontine structures.

Conclusion: Although eight-and-a-half syndrome is most commonly caused by an infarction or demyelination, in rare instances, a space-occupying lesion at the level of the pons can be the etiology. It is of utmost importance to recognize the features of this disease entity to be able to exhaust the proper diagnostic exams, localize the lesion and determine the proper treatment regimen catered to each patient.

Eight-and-a-half syndrome caused by a pontine haemorrhage: a case report and review of the literature

BACKGROUND

Eight-and-a-half syndrome is caused by a lesion in the dorsal tegmentum of the caudal pons involving parapontine reticular formation and median longitudinal fasciculus, as well as the nucleus and/or the fasciculus of the facial nerve. It is characterized by one-and-a-half syndrome and an ipsilateral cranial nerve VII palsy. Also, many variants of eight-and-a-half syndrome have been described, including nine syndrome, thirteen-and-a-half syndrome and fifteen-and-a-half syndrome.

METHODS

We describe a case of a 49-year-old man who presented with eight-and-a-half syndrome combined with contralateral hemiparesis. We reviewed the literature describing the related spectrum of eight-and-a-half syndrome associated with various etiologies.

RESULTS

Brain computed tomography scan revealed a hyperdensity located in the left paramedian aspect of the dorsal pons. T2-weighted magnetic resonance imaging at the 11-month follow-up showed hyperintensity and enlargement of the inferior olivary nuclei, which were compatible with a diagnosis of hypertrophic olivary degeneration. In light of our observations and cases reported in the literature, we categorize the spectrum of eight-and-a-half syndrome into three types, namely classic eight-and-a-half syndrome, eight-and-a-half syndrome variants and eight-and-a-half plus syndrome. Besides, the clinical feature and outcome of the three types are discussed in this article.

CONCLUSIONS

Recognition of the spectrum of eight-and-a-half syndrome allows precise anatomic localization of the lesion to pontine tegmentum region.

"Nine" syndrome: A new neuro-ophthalmologic syndrome: Report of two cases

“Eight-and-a-half” syndrome is a rare condition involving the ipsilateral abducens nucleus or paramedian pontine reticular formation (PPRF), the ipsilateral medial longitudinal fasciculus (MLF), and the adjacent facial colliculus/facial nerve fascicle. The condition is often caused by a lesion (vascular or demyelinating) in the dorsal tegmentum of the caudal pons. There are new variants of this syndrome caused by extension of lesion to involve new adjacent structures in pontine tegmentum. We report two patients with different etiology presenting with clinical features suggestive of eight-and-a-half syndrome associated with hemiataxia representing “nine” syndrome (8½ + ½ = 9) adding new dimension to “eight-and-a-half” syndrome.