Methanol Toxicity Clinical Presentation

  • Author: Kalyani Korabathina, MD; Chief Editor: Tarakad S Ramachandran, MBBS, FRCP(C), FACP   more...
 
Updated: Feb 3, 2012
 

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.[5]

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.[10] Further, motor neuron disease resembling amyotrophic lateral sclerosis has been documented in a case report.[11] 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 and American Epilepsy Society

Disclosure: Nothing to disclose.

Coauthor(s)

Selim R Benbadis, MD  Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, Tampa General Hospital, University of South Florida 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, and American Medical Association

Disclosure: UCB Pharma Honoraria Speaking, consulting; Lundbeck Honoraria Speaking, consulting; Cyberonics Honoraria Speaking, consulting; Glaxo Smith Kline Honoraria Speaking, consulting; Pfizer Honoraria Speaking, consulting; Sleepmed/DigiTrace Honoraria Speaking, consulting

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, and American Heart Association

Disclosure: Nothing to disclose.

Chief Editor

Tarakad S Ramachandran, MBBS, FRCP(C), FACP  Professor of Neurology, Clinical Professor of Medicine, Clinical Professor of Family Medicine, Clinical Professor of Neurosurgery, State University of New York Upstate Medical University; Chair, Department of Neurology, Crouse Irving Memorial Hospital

Tarakad S Ramachandran, MBBS, FRCP(C), FACP is a member of the following medical societies: American Academy of Neurology, American Academy of Pain Medicine, American College of Forensic Examiners, American College of International Physicians, American College of Managed Care Medicine, American College of Physicians, American Heart Association, American Stroke Association, Royal College of Physicians, Royal College of Physicians and Surgeons of Canada, Royal College of Surgeons of England, and Royal Society of Medicine

Disclosure: Abbott Labs None None; Teva Marion None None; Boeringer-Ingelheim Honoraria Speaking and teaching

Additional Contributors

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

References

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  2. Bitar ZI, Ashebu SD, Ahmed S. Methanol poisoning: diagnosis and management. A case report. Int J Clin Pract. Nov 2004;58(11):1042-4. [Medline].

  3. LeWitt PA, Martin SD. Dystonia and hypokinesis with putaminal necrosis after methanol intoxication. Clin Neuropharmacol. Apr 1988;11(2):161-7. [Medline].

  4. Coulter CV, Farquhar SE, McSherry CM, Isbister GK, Duffull SB. Methanol and ethylene glycol acute poisonings - predictors of mortality. Clin Toxicol (Phila). Dec 2011;49(10):900-6. [Medline].

  5. Rathi M, Sakhuja V, Jha V. Visual blurring and metabolic acidosis after ingestion of bootlegged alcohol. Hemodial Int. Jan 2006;10(1):8-14. [Medline].

  6. Casarett LJ, Doull J, Klaassen CD, eds. Casarett and Doull's Toxicology: The Basic Science of Poisons. 5th ed. New York, NY: McGraw-Hill; 1996:604-5, 756-7.

  7. Phang PT, Passerini L, Mielke B, et al. Brain hemorrhage associated with methanol poisoning. Crit Care Med. Feb 1988;16(2):137-40. [Medline].

  8. Jacobsen D, McMartin KE. Antidotes for methanol and ethylene glycol poisoning. J Toxicol Clin Toxicol. 1997;35(2):127-43. [Medline].

  9. Rosenstock L, Cullen MR, eds. Textbook of Clinical Occupational and Environmental Medicine. Philadelphia, Pa: WB Saunders; 1994:768.

  10. Hageman G, van der Hoek J, van Hout M, et al. Parkinsonism, pyramidal signs, polyneuropathy, and cognitive decline after long-term occupational solvent exposure. J Neurol. Mar 1999;246(3):198-206. [Medline].

  11. Chio A, Herrero Hernandez E, Mora G, et al. Motor neuron disease and optic neuropathy after acute exposure to a methanol-containing solvent mixture. Amyotroph Lateral Scler Other Motor Neuron Disord. Sep 2004;5(3):188-91. [Medline].

  12. Jacobsen D, McMartin KE. Methanol and ethylene glycol poisonings. Mechanism of toxicity, clinical course, diagnosis and treatment. Med Toxicol. Sep-Oct 1986;1(5):309-34. [Medline].

  13. Fujita M, Tsuruta R, Wakatsuki J, et al. Methanol intoxication: differential diagnosis from anion gap-increased acidosis. Intern Med. Aug 2004;43(8):750-4. [Medline].

  14. McKellar MJ, Hidajat RR, Elder MJ. Acute ocular methanol toxicity: clinical and electrophysiological features. Aust N Z J Ophthalmol. Aug 1997;25(3):225-30. [Medline].

  15. Blanco M, Casado R, Vazquez F, Pumar JM. CT and MR imaging findings in methanol intoxication. AJNR Am J Neuroradiol. Feb 2006;27(2):452-4. [Medline].

  16. Hantson P, Duprez T, Mahieu P. Neurotoxicity to the basal ganglia shown by magnetic resonance imaging (MRI) following poisoning by methanol and other substances. J Toxicol Clin Toxicol. 1997;35(2):151-61. [Medline].

  17. LoVecchio F, Sawyers B, Thole D, et al. Outcomes following abuse of methanol-containing carburetor cleaners. Hum Exp Toxicol. Oct 2004;23(10):473-5. [Medline].

  18. Sharma R, Marasini S, Sharma AK, Shrestha JK, Nepal BP. Methanol Poisoning: Ocular and Neurological Manifestations. Optom Vis Sci. Nov 28 2011;[Medline].

 
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