Lithium-induced downbeat nystagmus

Downbeat nystagmus: a clinical and pathophysiological review

Downbeat nystagmus (DBN) is a neuro-otological finding frequently encountered by clinicians dealing with patients with vertigo. Since DBN is a finding that should be understood because of central vestibular dysfunction, it is necessary to know how to frame it promptly to suggest the correct diagnostic-therapeutic pathway to the patient. As knowledge of its pathophysiology has progressed, the importance of this clinical sign has been increasingly understood. At the same time, clinical diagnostic knowledge has increased, and it has been recognized that this sign may occur sporadically or in association with others within defined clinical syndromes. Thus, in many cases, different therapeutic solutions have become possible. In our work, we have attempted to systematize current knowledge about the origin of this finding, the clinical presentation and current treatment options, to provide an overview that can be used at different levels, from the general practitioner to the specialist neurologist or neurotologist.

Paraneoplastic Syndrome Case Presented As Nystagmus and Ataxia

The incidence of paraneoplastic syndrome (PNS) is on the rise, attributed to the growing detection of antibody modalities in both the serum and cerebrospinal fluid (CSF). PNS can occur as different neurological symptoms. The revised guidelines streamline the diagnostic approach but identifying PNS still requires the detection of neurological manifestations concurrent with cancer, along with the presence of specific PNS autoantibodies.

Downbeat nystagmus: a clinical review of diagnosis and management

PURPOSE OF REVIEW

This review will extensively cover the clinical manifestations, causes, diagnostic evaluation, and management strategies of downbeat nystagmus (DBN).

RECENT FINDINGS

Historically, MRI to assess for structural lesions at the cervicomedullary junction has been the primary diagnostic test in the evaluation of DBN since the 1980s. In recent years, there is increasing awareness of nonstructural causes of DBN including gluten ataxia, nutritional deficiencies, and paraneoplastic syndromes, among others. Medical management with aminopyridines has become first-line therapy in addition to disease-specific therapies.

SUMMARY

DBN is a common form of acquired nystagmus and the differential diagnosis remains broad, including both benign and potentially fatal causes. For practical purposes, the causes can be categorized as structural vs. nonstructural with MRI as the ideal, initial diagnostic study to differentiate the two. General therapeutic options include pharmacotherapy to enhance Purkinje cell function, strabismus surgery or prisms to shift null points, and behavioural changes. Disease-specific treatment is necessarily broad, though a significant proportion of patients will be idiopathic.

Ophthalmic adverse effects of lithium

Lithium is the current mainstay treatment for both acute and maintenance management of bipolar disorders. However, its narrow therapeutic index and array of side effects, although well-documented, can be challenging to manage. Comparatively, the side effects of lithium that involve the ophthalmic structures are not as well established in the literature and only partially appreciated, which can potentially lead to noncompliance. In this article, an extensive literature review of lithium and its ophthalmic adverse effects were performed and comprehensively summarized. Based on the search, documented ophthalmic adverse effects of lithium include: exophthalmos; abnormal eye movements; ocular myasthenia gravis; papilledema; photophobia; and abnormal tear film, contributing to dry eye disease. Additional studies are anticipated to be helpful in expanding the current understanding of lithium and its adverse ophthalmic side effects and certainly warranted to fill the knowledge gap. Close interprofessional management between psychiatrists and ophthalmologists is expected to be beneficial in patient care.

A case of skew deviation and downbeat Nystagmus induced by Lithium

Background

Lithium salts have been commonly used for prophylaxis and treatment of bipolar disorder and have numerous side effects. However, there has been no report of skew deviation and downbeat nystagmus associated with lithium. Herein, we report the first case of lithium-induced skew deviation and downbeat nystagmus.

Case presentation

A 39 years-old woman presented with intermittent vertical diplopia and dizziness within 1–2 months. Ophthalmologic examination revealed downbeat nystagmus and 6 prism diopters of right hypertropia. Funduscopic examination showed mild incyclotorsion on right eye. However, ductions and versions were within normal range. Other neurological examinations were also normal. She had a history of bipolar disorder treated with daily 600-900 mg of lithium for past 6 years, and 2 months before the first visit, daily dose of lithium was increased to 1200 mg. We referred the patients to psychiatrist. Although the serum level of lithium was within the normal therapeutic range, her daily dose of lithium was reduced to 600 mg and then stopped. 6 days after cessation of lithium, down beat nystagmus and right hypertropia were completely resolved and symptoms did not recur over a year.

Conclusion

Even within a normal therapeutic range, downbeat nystagmus and skew deviation can occur as side effect of lithium. Dehydration may contribute to the neurotoxicity of lithium.

Reversible hand tremors, downbeat nystagmus, and an unsteady gait with nontoxic lithium level

Patients with nontoxic lithium levels can still develop hand tremors, downbeat nystagmus, and an unsteady gait.

Lithium-induced downbeat nystagmus

We report the case of a 76-year old lady under lithium carbonate for a bipolar disorder who presented with a suspected optic neuritis. A typical lithium-induced downbeat nystagmus was observed. Discontinuation of lithium therapy resulted in frank improvement in visual acuity and disappearance of the nystagmus.

Lithium-Induced Downbeat Nystagmus and Horizontal Gaze Palsy

We report a case of lithium-induced downbeat nystagmus and horizontal gaze palsy in a 62-year-old woman who was treated for a bipolar affective disorder with lithium carbonate for one month. At presentation serum lithium was within therapeutic range. No alternative causes of the ocular motility disturbances were found, and the patient improved significantly as lithium carbonate was discontinued.

Ocular adverse effects of common psychotropic agents: a review

All psychotropic medications have the potential to induce numerous and diverse unwanted ocular effects. Visual adverse effects can be divided into seven major categories: eyelid and keratoconjunctival disorders; uveal tract disorders; accommodation interference; angle-closure glaucoma; cataract/pigmentary deposits in the lens and cornea; retinopathy; and other disorders. The disorders of the eyelid and of the keratoconjunctiva are mainly related to phenothiazines and lithium. Chlorpromazine, at high dosages, can commonly cause abnormal pigmentation of the eyelids, interpalpebral conjunctiva and cornea. It can also cause a more worrisome but rarer visual impairment, namely corneal oedema. Lithium can rarely lead to a bothersome eye irritation by affecting sodium transport. Uveal tract problems are mainly associated with tricyclic antidepressants (TCAs), typical antipsychotics, topiramate and selective serotonin reuptake inhibitors (SSRIs). TCAs, typical antipsychotics and SSRIs can all cause mydriasis that is often transient and with no major consequences, but that can promote closure of angles in susceptible patients. Topiramate has been frequently associated with a number of significant ocular symptoms including acquired myopia and angle-closure glaucoma. Problems with accommodation are related to TCAs and to low-potency antipsychotics. TCAs cause transient blurred vision in up to one-third of patients. Angle-closure glaucoma is a serious condition that has been mainly associated with TCAs, low-potency antipsychotics, topiramate and, to a lesser extent, SSRIs. When patients with narrow angles are given TCAs, they all appear to experience induction of glaucomatous attacks. Antipsychotics and SSRIs may lead to an added risk of developing angle-closure glaucoma, but only in predisposed eyes. Topiramate can lead to an allergic-type reaction whereby structures of the lens and ciliary body are displaced, which results in angle-closure glaucoma. Cataractous changes can result from antipsychotics, mainly from high dosages of chlorpromazine or thioridazine. These two drugs, when used at high dosages and for prolonged periods, frequently cause lenticular opacifications. Retinopathy has been shown to be related to high dosages of typical antipsychotics, mainly chlorpromazine and thioridazine. The frequency of occurrence of retinal effects seems to be proportional to the total amount of drug used over a long period of time. Other visual problems of special concern are the ocular dystonias, other eye movement disorders, and decreased ability to perceive colours and to discriminate contrast. Ocular dystonias can occur with antipsychotics (especially high-potency ones), carbamazepine (especially in polytherapy), topiramate and, rarely, with SSRIs. Disturbance in various eye movements is frequently seen with benzodiazepines, antiepileptic drugs and lithium. Impairment in the perception of colours and the discrimination of contrasts has been shown to occur not uncommonly with carbamazepine and lorazepam. Thus, typical antipsychotics, TCAs, lithium, benzodiazepines, carbamazepine, topiramate and SSRIs appear to produce most of the currently recognized ocular problems. Psychiatrists, ophthalmologists and patients need to be aware of and prepared for any medication-induced adverse effect. Early prevention and intervention can avoid most of the serious and potentially irreversible ocular toxicities.

Evidence that perihypoglossal neurons involved in vestibular-auditory and gaze control functions respond to nerve growth factor

Nerve growth factor (NGF), which has long been considered to be a trophic factor for peripheral sensory and sympathetic neurons, has been found recently to influence cholinergic neurons in the basal forebrain and neostriatum. In the present study, we provide evidence that brainstem neurons in the perihypoglossal area that relay information from the inner ear and vestibular apparatus to the cerebellum and tectum are responsive to NGF. These neurons, which are located in the nucleus prepositus hypoglossi (NPH), spinal vestibular nucleus, cochlear complex, and gigantocellular and paragigantocellular nuclei of the reticular formation, express functional receptors for NGF and up-regulate the expression of trkA receptors after injection of NGF into targets. In addition, the developmental up-regulation of NGF in the cerebellum coincides with the differentiation of the perihypoglossal nuclei. These results suggest that neurons representing the principal brain relays for auditory and vestibular pathways and perihypoglossal neurons involved in gaze coordination are a novel group of central neurons (besides cholinergic neurons in the basal forebrain and neostriatum) that respond to NGF.

Ocular adverse effects of neuropsychiatric agents. Incidence and management

Neuropsychiatric agents may adversely affect the eye in various ways. The more frequently encountered effects include corneal oedema and pigmentary changes in the lens and cornea which are induced by phenothiazine derivatives; thioridazine-induced retinopathy; tricyclic antidepressant-induced accommodation interference and glaucoma; and lithium carbonate-induced exophthalmos and papilloedema. Several adverse effects, such as corneal oedema, retinopathy and glaucoma, are vision-threatening, and patients often fail to describe their symptoms properly. A more precise understanding of these conditions is essential for prompt diagnosis and appropriate treatment.

Neuro-ophthalmology and psychiatry

Neuro-ophthalmology and psychiatry interact over several issues. The neuro-ophthalmologist can confirm the suspicion of nonorganic visual dysfunction by demonstrating the functional integrity of the visual system and the nonphysiologic nature of the visual complaints. He or she may recognize evidence of organic dysfunction in the patient with a presumed psychiatric diagnosis. In some cases, the pathology may be related to the use of certain psychiatric medications. Specialized examination techniques within the realm of neuro-ophthalmology may provide subtle information about the functional integrity of the central nervous system in patients with psychiatric disease. Clinical and investigational collaboration between the neuro-ophthalmologist and the psychiatrist will provide the most appropriate patient management and may further our understanding of the biological basis of psychiatry.