User:Alphabetfood/"Grinker myelinopathy"

Grinker's Myelinopathy, also known as Anoxic Leukoencephalopathy and delayed post-hypoxic leukoencephalopathy (DPHL), is a rare disease of the Central Nervous System. Originally characterized by Roy R. Grinker Sr. in 1925, Grinker's Myelinopathy is characterized by a delayed leukoencephalopathy after a hypoxic episode. It is typically, though not necessarily, related to carbon monoxide poisoning or heroin overdose. It occurs in roughly 2.8% of those who experience an acute hypoxic/anoxic episode. Because of the wide range of symptoms and the delay in onset, it is often misdiagnosed as other neuropathologies.

Categorization

Following an apparent rehabilitation from a severe episode of prolonged cerebral oxygen deprivation, a patient begins to experience massive white matter death that leads to a wide range of neurological dysfunctions ranging from confusion and apathy to parkinson-like symptoms.

Onset

The onset of the symptoms usually occurs several weeks after the initial hypoxic episode. The hypoxic episode is necessarily severe, usually with an arterial oxygen partial pressure less than 40mmHg. Following the severe hypoxia, the patient typically falls unconscious or into a coma, with the exception of cases of CO poisoning. If the patient recovers from this unconscious state, usually within 24 hours, it is typically followed by a successful recovery over a few days (generally 4 to 5). After the short recovery a lucid period is seen, lasting anywhere from 1 to 4 weeks, in which the patient exhibits no symptoms related to the anoxic episode. It is after this period that the degenerative symptoms begin to appear rapidly and grow in severity.

Symptoms

The symptoms upon onset ave been known to include apathy, dementia, parkinsonism, agitation, urinary incontinence, and pseudobulbar palsy., among many other neuropsychiatric symptoms. Microscopically, extensive hemispheric demyelination and the degeneration of the basal ganglia are observed.

Diagnosis

Once other possible causes for dementia or hysteria have been eliminated Grinker's myelinopathy is diagnosed with a clinical history of carbon monoxide poisoning, narcotic overdose, myocardial infarction, or other global cerebral hypoxic event. This diagnosis can then be supported by neuroimaging confirmation of broadcast hemispheric demyelination sparing cerebellar and brainstem tracts. The neuroimaging evidence can also diagnose Grinker's myelinopathy through an elevated cerebrospinal fluid myelin basic protein.

Neuroimaging

While there are no standard criteria for the diagnosis of Grinker's Myelinopathy, neuroimaging can be an important diagnostic tool in ruling out other diagnoses. Magnetic resonance imaging (MRI) or computed tomography (CT) can be used to demonstrate a decrease in white matter density in the patient’s cerebral hemispheres, with the typical exception of overlying cortices. Unexplained, uniform demyelination of white matter can indicate acute onset Grinker's Myelinopathy.

Causes

Pathophisiology

The main cause of the neurological disorders is believed to be demyelination of the cerebral hemispheres, though there is currently no widely accepted consensus on why. The most commonly accepted theories for the cause of demyelination include carbon monoxide toxicity, cerebral blood vessel damage, cerebral edema, and a disruption of myelin-producing pathways.

The direct toxicity of carbon monoxide

Because carbon monoxide binds to hemoglobin more efficiently than oxygen and, lower systemic blood pressure brought upon by an acute anoxic episode in conjunction with CO poisoning often leads to cerebral ischemia, a condition where the brain does not receive enough oxygen to satisfy its needs. This results in lesions to a great deal of subcortical cerebral white matter but leaving axons, U-fibers, and perivascular myelin mostly untouched. Support against this theory stems from the ability to replicate these lesions by using nitrogen-induced hypoxia and hypotension in cats and the onset of this disease in individuals who experienced acute hypoxia without CO poisoning.

Cerebral edema

Cerebral edema, or unusual swelling of the brain, is commonly caused by anoxic episodes. If it is severe enough, it is known to cause preferential damage to cerebral white matter due to excessive swelling of glial cells while leaving many other tissues unharmed.

This theory suggests that hypoxia and carbon monoxide induce a form of edema resulting in white matter necrosis. Evidence for this theory comes from the observation of pathological lesions mimicking those of carbon monoxide poisoning where hypoxia and dehydration along with too-rapid rehydration have taken place without carbon monoxide present.

Disruption of myelin-creating pathways

The anoxic event is likely to cause damage to cytoplasmic ATP-dependent enzymes in oligodendrocytes. Because many of these enzymes play essential roles in myelin turnover, damage to these enzymes is thought to adversely affect the ability of the body to sustain myelin in white matter, leading to the demyleination of those areas of the brain. The inability to regenerate and remove myelin on certain cells is thought to be responsible for the delay in onset of the disease and for the specificity of the white matter death.

Prevention

One way to prevent the likelihood of Grinker's myelinoopathy occurring is standard or hyperbaric oxygen after carbon monoxide poisoning. Another preventative measure one can take is to be on bed rest and abstain from stressful and strenuous procedures for the first 10 days after an extended hypoxic event. Expectation and recognition will also lead to an earlier and more accurate and appropriate use of health care services.

Prognosis

Those patients who survive initial hospitalization are likely to recover from Grinker's Myelinopathy, but may take up to a year or longer. Age seems to be a factor in the severity of the disease, as one study indicated that the mean age of patients who recovered within one year was 10 years younger than that of patients who did not. For most patients, a recovery time of 3-6 months is typical. Even after recovering, however, some symptoms may persist, including cognitive deficits or parkinsonian symptoms that can be treated separately.

Alternative Names

Though originally characterized as Grinker's Myelinopathy, this disease has received many names, depending on the literature under which it is described, including:

• Delayed Post-Hypoxic Encephalopathy.
• Delayed Post-Hypoxic Leukoencephalopathy (DPHL)
• Delayed post-anoxic leukoencephalopathy
• Delayed post-anoxic encephalopathy
• Delayed post-hypoxic encephalopathy
• Delayed neurologic sequelae

History

Grinker's Myelinopathy is named after the pathologist Roy R. Grinker, who first described it in 1925.

References

Category:Neurological disorders Category:Anatomical pathology