Downbeat nystagmus with magnesium depletion

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.

How should I approach and manage adult-onset oscillopsia?

Oscillopsia is the sensation of illusory movement within the visual percept leading to a degradation of visual functioning and quality of life. The constellation of conditions manifesting with oscillopsia marks the overlap between ophthalmology and otorhinolaryngology. The purpose of this article is therefore to review the aetiologies of oscillopsia and provide pathways for investigation and treatment of processes that associate oscillopsia with intrusive ocular movement and for processes manifesting as oscillopsia in the absence of intrusive ocular movement. Points for referral are also included for the diagnoses that are more appropriately investigated and managed by allied medical specialties.

An atypical case of hypomagnesemia-induced cerebellar syndrome with literature review

Cerebellar ataxia in adults is always a diagnostic challenge. One of the important causes of late-onset cerebellar ataxia is hypomagnesemia. Hypomagnesemia can have varied manifestations and is attributable to numerous causes. Identification of hypomagnesemia-induced cerebellar syndrome (HiCS) is important as it is reversible but often missed. HiCS has distinct clinical findings and characteristic magnetic resonance imaging (MRI) findings. HiCS presents with distinct clinical, biochemical, and neuroimaging findings, but it cannot be ruled out even in the absence of neuroimaging findings. This condition has to be treated promptly and meticulously to avoid precipitating any serious complications, and a strong suspicion is required for the diagnosis. The underlying cause should be evaluated and managed, as HiCS is a serious but potentially reversible disease with a good prognosis. We present a case of HiCS presenting with a characteristic history of recurrent ataxia, tremor, and vertigo that improved with treatment. Our patient was atypical, as there were no significant MRI findings attributable to hypomagnesemia. Only seven case reports are available throughout the world that show such disparity.

Movement Disorders and Other Neurologic Impairment Associated With Hypomagnesemia: A Systematic Review

Purpose of Review

The objective of this study was to explore the clinical spectrum of movement disorders and associated neurologic findings in hypomagnesemia and challenges in diagnosis and treatment.

Recent Findings

Sixty patients were identified in the literature for analysis. Movement disorders observed were postural tremor (23.3%, n = 14), resting tremor (8.3%, n = 5), intention tremor (10%, n = 6), ataxia involving the trunk (48.3%, n = 29) or limbs (25%, n = 15) and dysarthria (21.7%, n = 13), athetosis (8.3%, n = 5), myoclonus (6.7%, n = 4), and chorea (1.8%, n = 1). Symptoms may be accompanied by downbeat nystagmus, tetany, drowsiness, vertigo, and proximal muscle weakness. Residual deficits were noted in 16 (26.67%) patients. Serum magnesium was 1.3 mg/dL or lower in 53 patients (88.3%). Imaging findings include bilateral cerebellar (20%, n = 11) and vermis hyperintensities (9.09%, n = 5) and normal imaging. Proton pump inhibitors are the commonest etiology.

Summary

The movement disorders linked with hypomagnesemia can be associated with varied neurologic symptoms. A high degree of suspicion will enable early diagnosis to prevent residual deficits.

Case report: Acute vestibular syndrome and cerebellitis in anti-Yo paraneoplastic syndrome

Background

We define acute vestibular syndrome (AVS) as a sudden onset vertigo, nausea, vomiting, and head motion intolerance, more frequently associated with an acute peripheral and unilateral vestibulopathy. About 10–20% of all cases with central vestibulopathy are secondary to stroke. We report three patients evaluated over the past decade with an acute AVS along with subtle downbeat nystagmus (DBN), followed by dysarthria and progressive truncal and limb ataxia, as well as increasing DBN intensity.

Methods

All patients underwent neurologic examination, video-oculography, MRI, serum cancer markers, spinal fluid examination, paraneoplastic panel testing, and oncologic workup. With a consolidated diagnosis of cancer/paraneoplastic syndrome, we treated with plasma exchange (PLEX), high-dose steroids, surgery, and oncologic investigation. We additionally provided oncotherapy in one out of three patients.

Results

All three patients had an acute AVS, downbeat nystagmus DBN, and inability to perform tandem gait. Two of three patients had a normal head impulse test (HIT). As acute vertigo, nausea, and vomiting subsided, a progressive cerebellar syndrome ensued characterized by persistent DBN, impaired horizontal and vertical pursuit, impaired VOR suppression, truncal and limb ataxia, and dysarthria. All patients had normal MRI brain studies excluding stroke. CSF studies demonstrated lymphocytic pleocytosis and elevated protein. One patient had confirmed ovarian cancer with high CA-125 serum levels; another had undifferentiated cancer of unknown primary with high CA-125 and one patient with esophageal cancer. All had a positive PCA-1 antibody titer, also known as anti-Yo antibody. In one patient with expeditious immunosuppression, the ataxia progression slowed for 18 months, whereas the other two patients with delayed initiation of treatment had more rapidly progressive ataxia.

Discussion

Paraneoplastic encephalitis related to PCA-1 antibody (Anti-Yo) targets Purkinje cells and cells in the granular layer of the cerebellar cortex. Clinically, our patients had a central AVS characterized by DBN and followed with progressive ataxia and unremarkable neuroimaging studies. Rapid initiation of treatment may offer a greater chance to prevent further neurologic decline. Any patient with an AVS as well as DBN and normal MRI should have an expeditious workup to rule out metabolic, toxic, and infectious causes just prior to considering prompt treatment with high-dose steroids and plasma exchange (PLEX) to mitigate the risk of rapidly progressive and irreversible neurologic decline.

Vestibular Disorders after Kidney Transplantation: Focus on the Pathophysiological Mechanisms Underlying the Vertical Nystagmus Associated with Tacrolimus-Related Hypomagnesamia

The purpose of this paper is to present the case of a patient undergoing kidney transplantation who developed limb tremor dizziness and vertical nystagmus (ny) during Tacrolimus (TAC) therapy and to investigate the pathophysiological mechanisms underlying the balance disorder. This case study regards a 51-year old kidney transplant male patient with hand tremors and lower limbs asthenia associated with dizziness and nausea. The symptoms started two months after the beginning of intravenous TAC for renal transplantation. The pure-tone audiometry showed a mild symmetrical high-frequencies down-sloping sensorineural hearing loss. Acoustic emittance measures showed a normal tympanogram; stapedial reflexes were normally elicited. The Auditory Brainstem Responses (ABR) and Cervical Vestibular Evoked Myogenic Potentials (c-VEMPs) were bilaterally normally evoked. The bedside vestibular examination showed spontaneous down-beating stationary persistent, omni-positional nystagmus, not inhibited by fixation. The Head-Shaking Test accentuates the spontaneous ny. The horizontal clinical head impulse test was negative, bilaterally. A biochemical blood test revealed a decrease in Magnesium (Mg) levels (0.8 mg/dL; normal range 1.58–2.55). The integration of Mg induced both a plasma levels normalization and an improvement of clinical symptoms. This case suggests that TAC treatment can induce a Mg depletion that caused the transient cerebellar lesion. Therefore, the monitoring of serum electrolytes during immunosuppressive treatment appears to be a useful tool in order to reduce the central system symptomatology.

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.

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.

Posterior Reversible Encephalopathy Syndrome due to Hypomagnesemia: A Case Report and Literature Review

Background

Hypomagnesemia can cause various unspecific neurological complications, which can lead to diagnostic confusion. One of these complications is the posterior reversible encephalopathy syndrome (PRES), which is extremely uncommon and has been reported only twice in the English-language literature.

Case presentation

We report the case of a 60-year-old man who presented with PRES involving only the cerebellar hemispheres and associated with hypomagnesemia. After excluding all the other possible etiologies of PRES, we started magnesium replacement therapy, which led to a remarkable but fluctuating clinical and chemical improvement. A full recovery with no need for further supplementation was achieved only after discontinuation of a proton pump inhibitor.

Conclusions

This case highlights the role of magnesium in the pathophysiology of PRES; thereby, underlying hypomagnesemia should be considered in every PRES case with unclear etiology.

Hypomagnesemia in critically ill patients

BACKGROUND

Magnesium (Mg) is essential for life and plays a crucial role in several biochemical and physiological processes in the human body. Hypomagnesemia is common in all hospitalized patients, especially in critically ill patients with coexisting electrolyte abnormalities. Hypomagnesemia may cause severe and potential fatal complications if not timely diagnosed and properly treated, and associate with increased mortality.

MAIN BODY

Mg deficiency in critically ill patients is mainly caused by gastrointestinal and/or renal disorders and may lead to secondary hypokalemia and hypocalcemia, and severe neuromuscular and cardiovascular clinical manifestations. Because of the physical distribution of Mg, there are no readily or easy methods to assess Mg status. However, serum Mg and the Mg tolerance test are most widely used. There are limited studies to guide intermittent therapy of Mg deficiency in critically ill patients, but some empirical guidelines exist. Further clinical trials and critical evaluation of empiric Mg replacement strategies is needed.

CONCLUSION

Patients at risk of Mg deficiency, with typical biochemical findings or clinical symptoms of hypomagnesemia, should be considered for treatment even with serum Mg within the normal range.

Cardiac Dysrhythmias and Neurological Dysregulation: Manifestations of Profound Hypomagnesemia

Magnesium is the second most common intracellular cation and serves as an important metabolic cofactor to over 300 enzymatic reactions throughout the human body. Among its various roles, magnesium modulates calcium entry and release from sarcoplasmic reticulum and regulates ATP pumps in myocytes and neurons, thereby regulating cardiac and neuronal excitability. Therefore, deficiency of this essential mineral may result in serious cardiovascular and neurologic derangements. In this case, we present the clinical course of a 76-year-old woman who presented with marked cardiac and neurological signs and symptoms which developed as a result of severe hypomagnesemia. The patient promptly responded to magnesium replacement once the diagnosis was established. We herein discuss the clinical presentation, pathophysiology, diagnosis, and management of severe hypomagnesemia and emphasize the implications of magnesium deficiency in the cardiovascular and central nervous systems. Furthermore, this case highlights the importance of having high vigilance for hypomagnesemia in the appropriate clinical setting.

Reversible hypomagnesaemia-induced subacute cerebellar syndrome

Magnesium is the second most abundant intracellular cation and is a fundamental cofactor in a multitude of cellular enzymatic reactions. Magnesium deficiency causes diverse clinical features predominantly due to cardio- and neurotoxicity. We describe a case of severe hypomagnesaemia associated with intermittent downbeat nystagmus, cerebellar ataxia, generalised convulsions and a supraventricular tachycardia. On MRI imaging, a transient lesion of the cerebellar nodulus was observed, which has not, to our knowledge, been previously described in isolated hypomagnesaemia.

Isolated familial hypomagnesaemia with novel neurological features: causal link or chance concurrence?

We report a patient with isolated familial hypomagnesaemia with hypocalciuria, a rare congenital disorder of magnesium metabolism. During adolescence the patient developed neurological and ophthalmological features not hitherto reported in this condition, including seizures, myoclonus, and retinal pigmentary degeneration. These suggested the phenotype of mitochondrial disease, which has been occasionally reported in association with hypomagnesaemia, but subsequent investigations of mitochondrial function were normal. The pathogenesis of this unusual neurological and ophthalmological syndrome therefore remains uncertain.

Lithium-induced downbeat nystagmus

We examined six patients who developed blurring or oscillopsia as a result of downbeat nystagmus while being treated with lithium carbonate. Of these six plus six previously described similar patients, all but two developed downbeat nystagmus insidiously as an isolated disorder in the setting of otherwise satisfactory therapeutic control, without clinical or biochemical evidence of acute lithium intoxication. Only six of these 12 patients were able either to reduce or to stop taking lithium, and in only two of these six did the downbeat nystagmus improve or remit.

Two cases of downbeat nystagmus and oscillopsia associated with carbamazepine

Downbeat nystagmus is often associated with structural lesions at the craniocervical junction, but has occasionally been reported as a manifestation of metabolic imbalance or drug intoxication. We recorded the eye movements of two patients with reversible downbeat nystagmus related to carbamazepine therapy. The nystagmus of both patients resolved after reduction of the serum carbamazepine levels. Neuroradiologic investigations including magnetic resonance imaging scans in both patients showed no evidence of intracranial abnormality. In patients with downbeat nystagmus who are taking anticonvulsant medications, consideration should be given to reduction in dose before further investigation is undertaken.

The use of clonazepam in the treatment of nystagmus-induced oscillopsia

The effect of clonazepam was studied in ten patients with nystagmus-induced oscillopsia due to downbeating or other primary position nystagmus. A 1-2-mg single-dose clonazepam test was used to determine whether long-term clonazepam therapy was indicated and to help distinguish between visual loss from underlying retinal or optic nerve disease and visual loss due to the nystagmus itself. With the single-dose clonazepam test, nystagmus was eliminated in 6 of 10 patients in the primary position of gaze and in 7 of 10 patients in downgaze. In all positions of gaze in all patients there was significant reduction in nystagmus intensity and slow phase velocity. Symptoms of oscillopsia were reduced or eliminated in all patients, and 7 of 8 patients with reduced visual acuity had clinical improvement. Guidelines are presented for the use of clonazepam in a single-dose clonazepam test and for long-term therapy.

Downbeat nystagmus indicates cerebellar or brain-stem lesions in vitamin B12 deficiency

Two cases of vitamin B12 deficiency caused by gastric atrophy are described. Together with the neuropsychiatric features usually associated with this condition, a downbeat nystagmus syndrome was observed. It is concluded that vitamin B12 deficiency may also result in lesions to those cerebellar or brain-stem structures that are generally assumed to cause downbeat nystagmus.

Formed visual hallucinations after metrizamide myelography

About 12 hours after 77-year-old woman underwent metrizamide myelography of the posterior fossa to elucidate the cause of downbeat nystagmus, she developed formed visual hallucinations consisting primarily of brightly colored geometric shapes, cloud formations, and human figures. Her white blood cell count was 26,000/mm3 and her serum creatine phosphokinase level was markedly increased to 438 units/liter. Two days later, the hallucinations had subsided, the white blood cell count had decreased to 17,000/mm3, and the serum creatine phosphokinase level had decreased to 105 units/liter. The hallucinations were probably caused by penetration of the metrizamide into the temporal lobe and visual association cortex.

Downbeat nystagmus with a pseudocycloid waveform: improvement with base-out prisms

Downbeat nystagmus in primary position and oscillopsia resulted from nutritional deficiency during prolonged intravenous therapy of a patient with hyperemesis gravidarum. Wide bandwidth infrared oculography demonstrated a pseudocycloid nystagmus waveform with an increasing-velocity exponential slow phase. Because the oscillopsia decreased and the nystagmus was damped with convergence, visual acuity improved with the addition of base-out prisms to each spectacle lens.