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Methanol Toxicity Clinical Presentation

  • Author: Kalyani Korabathina, MD; Chief Editor: Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS  more...
 
Updated: Mar 30, 2016
 

History

A careful history should be taken in high-risk patients who report typical symptoms of methanol poisoning.

Time course

Initial symptoms generally occur 12-24 hours after ingestion. The interval between ingestion and the appearance of symptoms correlates to the volume of methanol ingested and the amount of ethanol concomitantly ingested; competitive inhibition exists between the 2 compounds.[8]

Methanol blood levels peak at 30-90 minutes following ingestion and often do not correlate to the time to symptom appearance.

Neurologic manifestations

Initially, the symptoms of methanol intoxication are similar to those of ethanol intoxication, often with disinhibition and ataxia. Following a latent period, patients may develop headache, nausea, vomiting, or epigastric pain. In later stages, drowsiness may rapidly progress to obtundation and coma.

Seizures may occur, generally as a complication of the metabolic derangement or as a result of damage to the brain parenchyma.

Cases of axonal polyneuropathy in association with chronic exposure have been reported.[13] Further, motor neuron disease resembling amyotrophic lateral sclerosis has been documented in a case report.[14] It is likely that neuropathies and spinal cord dysfunction are underestimated.

Vision loss

Blindness from methanol inhalation was described as early as 1910. Formic acid accumulates within the optic nerve, which results in the classic visual symptoms of flashes of light and blurring.

Patients initially may present with diminished visual acuity, which can progress to scotomata and scintillations. The frank blindness that develops sometimes responds to immediate therapy; however, complete loss of vision is a common sequela.

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Physical Examination

Physical examination helps to rule out other causes of altered mental status and visual dysfunction, the 2 most common presenting signs of methanol intoxication. In cases of altered mental status and intentional overdose, the diagnosis of methanol intoxication may be difficult without a high clinical index of suspicion.

General physical examination

During the initial phase of methanol poisoning, individuals may experience effects similar to inebriation with alcohol and thus may not seek medical attention. As symptoms develop, most signs are related to metabolic acidosis; these are manifested as tachycardia, tachypnea, hypertension, and altered mental status. Pulmonary edema and acute respiratory distress may ensue, requiring intubation.

With large ingestions of methanol, depressed cardiac contractility heralds circulatory collapse and leads to signs of heart failure, cardiac arrhythmias, or both.

Neurologic examination

In addition to the progression of symptoms from drowsiness to stupor to coma, ocular findings in patients with methanol poisoning are prominent during a careful neurologic examination.

Visual symptoms necessitate a thorough examination of the fundi. Optic disc hyperemia occurs early in the course of methanol intoxication. Pupillary response to light is compromised and, subsequently, is lost. Little or no retinal damage is observed.

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Contributor Information and Disclosures
Author

Kalyani Korabathina, MD Consulting Physician, North County Neurology Associates, Inc

Kalyani Korabathina, MD is a member of the following medical societies: American Academy of Neurology, American Epilepsy Society

Disclosure: Nothing to disclose.

Coauthor(s)

David Likosky, MD Director of Stroke Program, President of Medical Staff, Evergreen Hospital Medical Center

David Likosky, MD is a member of the following medical societies: American Academy of Neurology, American College of Physicians-American Society of Internal Medicine, American Heart Association

Disclosure: Nothing to disclose.

Selim R Benbadis, MD Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, Tampa General Hospital, University of South Florida Morsani College of Medicine

Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, American Medical Association

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Cyberonics; Eisai; Lundbeck; Sunovion; UCB; Upsher-Smith<br/>Serve(d) as a speaker or a member of a speakers bureau for: Cyberonics (Livanova); Eisai; Lundbeck; Sunovion; UCB<br/>Received research grant from: Cyberonics (Livanova); GW, Lundbeck; Sunovion; UCB; Upsher-Smith.

Chief Editor

Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS Professor Emeritus of Neurology and Psychiatry, Clinical Professor of Medicine, Clinical Professor of Family Medicine, Clinical Professor of Neurosurgery, State University of New York Upstate Medical University; Neuroscience Director, Department of Neurology, Crouse Irving Memorial Hospital

Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS is a member of the following medical societies: American College of International Physicians, American Heart Association, American Stroke Association, American Academy of Neurology, American Academy of Pain Medicine, American College of Forensic Examiners Institute, National Association of Managed Care Physicians, American College of Physicians, Royal College of Physicians, Royal College of Physicians and Surgeons of Canada, Royal College of Surgeons of England, Royal Society of Medicine

Disclosure: Nothing to disclose.

Acknowledgements

Nestor Galvez-Jimenez, MD, MSc, MHA Chairman, Department of Neurology, Program Director, Movement Disorders, Department of Neurology, Division of Medicine, Cleveland Clinic Florida

Nestor Galvez-Jimenez, MD, MSc, MHA is a member of the following medical societies: American Academy of Neurology, American College of Physicians, and Movement Disorders Society

Disclosure: Nothing to disclose.

Jonathan S Rutchik, MD, MPH Assistant Professor, Department of Occupational and Environmental Medicine, University of California at San Francisco

Jonathan S Rutchik, MD, MPH is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, American College of Occupational and Environmental Medicine, and Society of Toxicology

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

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