Upbeat Nystagmus From a Demyelinating Lesion in the Caudal Pons

Upbeat Nystagmus with an Unusual Velocity-Decreasing and Increasing Waveform: a Sign of Gaze-Holding Dysfunction in the Paramedian Tracts in the Medulla?

We report a patient with spontaneous upbeat nystagmus (UBN) due to an ischemic lesion involving the paramedian tract (PMT) in the medulla. Eye movement recordings, using an infrared video-oculography (VOG) system, showed that the slow phase of the nystagmus was initially velocity-decreasing but gradually became velocity-increasing. Simulation of the nystagmus with a mathematical model supports a role for the PMT in relaying premotor signals for vertical gaze holding to the cerebellum. Our model shows that the disruption in cerebellar input from PMT can lead to the velocity-increasing waveform of the nystagmus, whereas the velocity-decreasing waveform could be related to a mismatch between the innervational commands to the ocular muscles (the pulse and step) needed to hold gaze steady.

Central Ocular Motor Disorders: Clinical and Topographic Anatomical Diagnosis, Syndromes and Underlying Diseases

The key to the diagnosis of ocular motor disorders is a systematic clinical examination of the different types of eye movements, including eye position, spontaneous nystagmus, range of eye movements, smooth pursuit, saccades, gaze-holding function, vergence, optokinetic nystagmus, as well as testing of the function of the vestibulo-ocular reflex (VOR) and visual fixation suppression of the VOR. This is like a window which allows you to look into the brain stem and cerebellum even if imaging is normal. Relevant anatomical structures are the midbrain, pons, medulla, cerebellum and rarely the cortex. There is a simple clinical rule: vertical and torsional eye movements are generated in the midbrain, horizontal eye movements in the pons. For example, isolated dysfunction of vertical eye movements is due to a midbrain lesion affecting the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), with impaired vertical saccades only or vertical gaze-evoked nystagmus due to dysfunction of the Interstitial nucleus of Cajal (INC). Lesions of the lateral medulla oblongata (Wallenberg syndrome) lead to typical findings: ocular tilt reaction, central fixation nystagmus and dysmetric saccades. The cerebellum is relevant for almost all types of eye movements; typical pathological findings are saccadic smooth pursuit, gaze-evoked nystagmus or dysmetric saccades. The time course of the development of symptoms and signs is important for the diagnosis of underlying diseases: acute: most likely stroke; subacute: inflammatory diseases, metabolic diseases like thiamine deficiencies; chronic progressive: inherited diseases like Niemann-Pick type C with typically initially vertical and then horizontal saccade palsy or degenerative diseases like progressive supranuclear palsy. Treatment depends on the underlying disease. In this article, we deal with central ocular motor disorders. In a second article, we focus on clinically relevant types of nystagmus such as downbeat, upbeat, fixation pendular, gaze-evoked, infantile or periodic alternating nystagmus. Therefore, these types of nystagmus will not be described here in detail.

Utilization of video oculography to quantify oculomotor dysfunction in anti-DPPX encephalitis: A case study

Anti-DPPX encephalitis is an increasingly recognized cause of neurological disability. We describe a case of a 44 year-old woman who presented to our facility with the chief complaint of confusion, weight loss, and a visual disturbance. Multidirectional nystagmus was noted, and she underwent additional evaluation. Anti-DPPX antibodies returned positive, and she treated with immunotherapy with improvement in her symptoms and deficits. We describe the video-oculography findings in the case, and discuss the implications for localization.

Ocular Motor Dysfunction Due to Brainstem Disorders

BACKGROUND

The brainstem contains numerous structures including afferent and efferent fibers that are involved in generation and control of eye movements.

EVIDENCE ACQUISITION

These structures give rise to distinct patterns of abnormal eye movements when damaged. Defining these ocular motor abnormalities allows a topographic diagnosis of a lesion within the brainstem.

RESULTS

Although diverse patterns of impaired eye movements may be observed in lesions of the brainstem, medullary lesions primarily cause various patterns of nystagmus and impaired vestibular eye movements without obvious ophthalmoplegia. By contrast, pontine ophthalmoplegia is characterized by abnormal eye movements in the horizontal plane, while midbrain lesions typically show vertical ophthalmoplegia in addition to pupillary and eyelid abnormalities.

CONCLUSIONS

Recognition of the patterns and characteristics of abnormal eye movements observed in brainstem lesions is important in understanding the roles of each neural structure and circuit in ocular motor control as well as in localizing the offending lesion.

Ocular Motor Manifestations of Multiple Sclerosis

BACKGROUND

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system leading to disability, especially in young patients. Acute or chronic lesions of MS within the brainstem and the cerebellum frequently result in ocular motor disorders.

EVIDENCE ACQUISITION

This review encompasses the spectrum of ocular motor disorders in patients with MS emphasizing prevalence, examination findings, diagnostic features, functional consequences, classification of MS course, and management of these disturbances of ocular motility.

RESULTS

Ocular motor manifestations of MS can occur acutely in relapse or chronically, the latter as a consequence of previous relapses or as a chronic course of the disease. The most frequent and specific acute ocular motor manifestation is uni- or bilateral internuclear ophthalmoplegia (INO). The most frequent chronic manifestations include INO and cerebellar ocular motor disorders such as gaze-evoked nystagmus, saccadic hypermetria, and lack of vestibulo-ocular reflex inhibition. The most disabling syndrome is pendular nystagmus.

CONCLUSIONS

The high prevalence of ocular motor manifestations emphasizes the importance of neuro-ophthalmological examination among patients with MS. Because chronic manifestations may cause minimal or no symptoms, a systematic investigation of the most common manifestations should be performed in daily practice. Appropriate treatment may improve visual outcome in some of these ocular motor disorders.

Downbeat nystagmus elicited by eyelid closure

We describe a patient with downbeat nystagmus (DBN) evoked only by eye closure. Brain and spinal cord magnetic resonance imaging revealed a T2 paramedian lesion in the left lower basis pontis and other white matter lesions consistent with multiple sclerosis. One potential mechanism for DBN in this case involves transverse ephaptic spread of excitation from areas that subserve coordinated lid closure to the decussating ventral tegmental tract.