eMedicine Specialties > Neurology > Neurotoxicology

Methanol: Follow-up

Author: Kalyani Korabathina, MD, Consulting Physician, North County Neurology Associates, Inc., Oceanside, California
Coauthor(s): Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital; David Likosky, MD, Clinical Instructor, Department of Neurology, University of Washington
Contributor Information and Disclosures

Updated: Nov 9, 2009

Follow-up

Complications

  • Vision loss
    • The mechanism by which the methanol causes toxicity to the visual system is not well understood. Formic acid, the toxic metabolite, is responsible for ocular toxicity in animal models and is rightly presumed to be responsible in human studies.
    • Serum methanol levels of greater than 20 mg/dL correlate with ocular injury. Funduscopic changes are notable within only a few hours after methanol ingestion and range from retinal edema in the perimacular region to the entire fundus. Optic disc edema and hyperemia is observed within 48 hours.
    • Visual injury may be prevented with prompt antidote therapy or via elimination of the metabolites from the system with hemodialysis; however, this is not always the case.
  • Movement disorders
    • Parkinsonian motor impairment has been described in some long-term survivors of methanol poisoning. This is thought to be due to the predilection for high concentrations of formic acid to accumulate within the putamen, but the reasons for this are unclear. One proposed reason is that formic acid has the ability to impair dopaminergic pathways and increase enzymatic activity of dopa-B-hydroxylase.13
    • Symptom onset is usually delayed several weeks after methanol exposure.
    • Common parkinsonian symptoms, such as tremor, cogwheel rigidity, stooped posture, shuffling gait, and hypokinesis, have been well described. In addition, dystonia and corticospinal tract signs have been established.
    • Several case reports have indicated symptom response with standard antiparkinsonian agents, particularly levodopa, amantadine, and bromocriptine.14
  • Muscle spasms have also been reported. As expected, these symptoms respond poorly to traditional therapy.4

Prognosis

Prognosis correlates with amount of methanol consumed and the subsequent degree of metabolic acidosis. This is further dependent on the amount of formic acid that has accumulated in the blood. Little long-term improvement can be expected in patients with neurologic complications.

Miscellaneous

Medicolegal Pitfalls

  • Diagnosis is the most important part of treating methanol poisoning.
  • In cases of stupor of unknown cause, testing for an osmolar gap should be routine. This enables early recognition and treatment of methanol intoxication.
  • In addition, a careful history should be taken in high-risk patients who report typical symptoms.
 


More on Methanol

Overview: Methanol
Differential Diagnoses & Workup: Methanol
Treatment & Medication: Methanol
Follow-up: Methanol
References
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References

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Further Reading

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Keywords

organic solvent, formaldehyde, alcohol dehydrogenase, methanol ingestion, methanol toxicity, methanol intoxication, antifreeze ingestion, perfume ingestion, paint solvent ingestion, inhalation of methanol, methanol fumes, methanol poisoning

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Contributor Information and Disclosures

Author

Kalyani Korabathina, MD, Consulting Physician, North County Neurology Associates, Inc., Oceanside, California
Kalyani Korabathina 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, University of South Florida School of Medicine, Tampa General Hospital
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: Nothing to disclose.

David Likosky, MD, Clinical Instructor, Department of Neurology, University of Washington
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.

Medical Editor

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.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

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.

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  Honoraria Consulting; Teva Marion Honoraria Consulting; Boeringer-Ingelheim Honoraria Speaking and teaching

 
 
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