The process of demyelination in the central nervous system. IV. Demyelination as a delayed residual of carbon monoxide asphyxia

Understanding a role for hypoxia in lesion formation and location in the deep and periventricular white matter in small vessel disease and multiple sclerosis

The deep and periventricular white matter is preferentially affected in several neurological disorders, including cerebral small vessel disease (SVD) and multiple sclerosis (MS), suggesting that common pathogenic mechanisms may be involved in this injury. Here we consider the potential pathogenic role of tissue hypoxia in lesion development, arising partly from the vascular anatomy of the affected white matter. Specifically, these regions are supplied by a sparse vasculature fed by long, narrow end arteries/arterioles that are vulnerable to oxygen desaturation if perfusion is reduced (as in SVD, MS and diabetes) or if the surrounding tissue is hypoxic (as in MS, at least). The oxygen crisis is exacerbated by a local preponderance of veins, as these can become highly desaturated 'sinks' for oxygen that deplete it from surrounding tissues. Additional haemodynamic deficiencies, including sluggish flow and impaired vasomotor reactivity and vessel compliance, further exacerbate oxygen insufficiency. The cells most vulnerable to hypoxic damage, including oligodendrocytes, die first, resulting in demyelination. Indeed, in preclinical models, demyelination is prevented if adequate oxygenation is maintained by raising inspired oxygen concentrations. In agreement with this interpretation, there is a predilection of lesions for the anterior and occipital horns of the lateral ventricles, namely regions located at arterial watersheds, or border zones, known to be especially susceptible to hypoperfusion and hypoxia. Finally, mitochondrial dysfunction due to genetic causes, as occurs in leucodystrophies or due to free radical damage, as occurs in MS, will compound any energy insufficiency resulting from hypoxia. Viewing lesion formation from the standpoint of tissue oxygenation not only reveals that lesion distribution is partly predictable, but may also inform new therapeutic strategies.

Hemin rescues adrenodoxin, heme a and cytochrome oxidase activity in frataxin-deficient oligodendroglioma cells

Mutations in the frataxin gene cause neurodegeneration and demyelination in Friedreich's ataxia. We showed earlier that frataxin deficiency causes primary iron-sulfur cluster defects, and later causes defects in heme and cytochrome c hemoprotein levels. Iron-sulfur (Fe/S) clusters are required in two enzymes of heme biosynthesis in humans i.e. in ferrochelatase and adrenodoxin. However, decreases in ferrochelatase activity have not been observed in frataxin-deficient HeLa cells or patient lymphoblasts. We knocked down frataxin in oligodendroglioma cells using siRNA, which produced significant defects in the activity of the Fe/S cluster enzymes adrenodoxin and aconitase, the adrenodoxin product heme a, and cytochrome oxidase, for which heme a serves as a prosthetic group. Exogenous hemin produced a significant rescue of adrenodoxin, aconitase, heme a levels and cytochrome oxidase activity. Thus hemin rescues iron-sulfur cluster defects that are the result of frataxin-deficiency, perhaps as a consequence of increasing the pool of bioavailable iron, and thus should be more fully tested for beneficial effects in Friedreich's ataxia models.

Carbon monoxide poisoning--a public health perspective

Carbon monoxide (CO) may be the cause of more than one-half of the fatal poisonings reported in many countries; fatal cases also are grossly under-reported or misdiagnosed by medical professionals. Therefore, the precise number of individuals who have suffered from CO intoxication is not known. The health effects associated with exposure to CO range from the more subtle cardiovascular and neurobehavioral effects at low concentrations to unconsciousness and death after acute or chronic exposure to higher concentrations of CO. The morbidity and mortality resulting from the latter exposures are described briefly to complete the picture of CO exposure in present-day society. The symptoms, signs, and prognosis of acute CO poisoning correlate poorly with the level of carboxyhemoglobin (COHb) measured at the time of hospital admission; however, because CO poisoning is a diagnosis frequently overlooked, the importance of measuring COHb in suspicious settings cannot be overstated. The early symptoms (headache, dizziness, weakness, nausea, confusion, disorientation, and visual disturbances) also have to be emphasized, especially if they recur with a regular periodicity or in the same environment. Complications occur frequently in CO poisoning. Immediate death is most likely cardiac in origin because myocardial tissues are most sensitive to the hypoxic effects of CO. Severe poisoning results in marked hypotension, lethal arrhythmias, and electrocardiographic changes. Pulmonary edema may occur. Neurological manifestation of acute CO poisoning includes disorientation, confusion, and coma. Perhaps the most insidious effect of CO poisoning is the development of delayed neuropsychiatric impairment within 2-28 days after poisoning and the slow resolution of neurobehavioral consequences. Carbon monoxide poisoning during pregnancy results in high risk for the mother by increasing the short-term complication rate and for the fetus by causing fetal death, developmental disorders, and chronic cerebral lesions. In conclusion, CO poisoning occurs frequently; has severe consequences, including immediate death; involves complications and late sequelae; and often is overlooked. Efforts in prevention and in public and medical education should be encouraged.

DIFFUSE DEGENERATION OF CEREBRAL WHITE MATTER RESEMBLING SOCALLED BINSWANGER'S DISEASE AND SYMMETRICAL NECROSIS OF THE GLOBUS PALLIDUS ASSOCIATED WITH ACUTE PORPHYRIA AND CEREBRAL ATHEROSCLEROSIS

A 59-year-old woman admitted to hospital in coma also showed generalized muscular rigidity and porphyria. After two days she became fully conscious but the muscular rigidity increased and persisted until death occurred 12 weeks later. The brain showed diffuse degeneration of the white matter; symmetrical necrosis of the globus pallidus was associated with severe localized atherosclerosis. The lesions probably resulted from the combined effects of porphyria and atherosclerosis. It is suggested that in later life unusual cerebral lesions may occur with porphyria because of associated atherosclerosis. The porphyria may be overlooked clinically.

MRI of cerebellar white matter damage due to carbon monoxide poisoning: case report

Extensive bilateral cerebellar white matter signal change, with sparing of the overlying cortex, consistent with demyelination was seen in a 12-year-old boy who had suffered carbon monoxide poisoning 6 years previously. His youth at the time of exposure and the long delay between exposure and examination might account for this unusual finding.

Neurological sequelae following carbon monoxide poisoning clinical course and outcome according to the clinical types and brain computed tomography scan findings

The prognosis for patients who survive carbon monoxide (CO) poisoning is uncertain, particularly in those who develop persistent neurological complications after recovery from the initial coma. Thirty-one patients with the sequelae of CO poisoning, followed for a year, are described. Eight had a progressive course, and 23 had a delayed relapse after an initial recovery period of approximately 20 days (range, 1-36 days). Those with a progressive course developed a persistent akinetic-mute state, and four of the eight died. Those with the delayed relapsing course either developed a parkinsonian state with behavioral and cognitive impairment but could walk (nine cases), or progressed further to an akinetic-mute state, and were bed-bound (14 cases); the deterioration to either condition occurred rapidly over a few days to a week. Fourteen of the patients with the delayed relapses (61%) subsequently improved, but three (13%) died. Those with a progressive course without initial recovery were younger (mean age, 37.0 years) than those with a delayed relapsing course (55.2 years; p < 0.01). The mean duration of their initial coma (9.8 days) was longer than that in delayed relapsing cases (2.0 days; p < 0.01). The mean initial CO hemoglobin level was not different in the two groups. Brain computed tomography (CT) scans were obtained at the onset of sequelae in both groups. Ten patients had a normal CT scan, 13 had white matter low-density lesions, and four had globus pallidus low-density lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Delayed encephalopathy following cardiac arrest

A 46 year old woman suffered a post-operative cardiac arrest associated with prolonged depression of oxygenation and respiration. She made a good initial recovery but one year later insidiously developed symptoms of widespread central nervous system damage compatible with a delayed post-hypoxic encephalopathy. This case is unusual in the length of time between the hypoxic insult and the later deterioration and also illustrates other atypical features of a delayed post-hypoxic syndrome.

Delayed encephalopathy following carbon monoxide intoxication

The case history and CT scan of a patient with delayed encephalopathy following carbon monoxide intoxication are described. The patient recovered. The CT scan revealed symmetrical areas of decreased density at the level of the globus pallidus. This case differs in several ways from other cases of carbon monoxide intoxication in which abnormalities of the CT scan were found.

Methanol poisoning: a clinical and pathological study

We report 2 survivors of severe methanol poisoning who developed, apart from blindness, a Parkinson-like extrapyramidal syndrome characterized by reduced initiative, poor voice volume, masked facies, mild tremor, rigidity, and bradykinesia. Both patients were mildly demented and 1 had hyperreflexia and bilateral Babinski responses. Computed tomographic scans in both patients demonstrated bilateral symmetrical infarction of the frontocentral white matter and putamen. Electromyography in 1 patient showed extensive denervation, mainly involving the legs, but normal motor conduction velocities. L-Dopa administered to the more severely affected patient had no effect on the parkinsonian features. Autopsy revealed cystic resorption of the putamen and the frontocentral subcortical white matter in additon to widespread neuronal damage throughout the cerebrum, cerebellum, brainstem, and spinal cord.

[Myelinopathy due to carbon monoxyde poisoning. A study in ultrastructural neuropathology (author's transl)]

A 24-year-old woman was found comatose after 2 days of cephalalgia and vomiting. An immediate diagnosis of carbon monoxyde poisoning was disclaimed when blood carbon monoxyde was found to be 1.75 ml/100. A diagnosis of acute intracranial hypertension led to trephination with ventricular punction and brain biopsy on the third day. The patient died on the eleventh day. Ultrastructural study of biopsy tissue showed nearly normal cortex, and injured white matter, with disrupted or destroyed myelin and pycnotic oligodendroglia in contrast with nearly normal axons, astrocytes, and capillaries. Autopsy showed a typical semioval center myelinopathy. After discussion of the histotoxic, vascular, and edema theories for myelinopathy pathogenesis, primary oligodendrogial lesion is considered, and correlated with the diphasic evolution often observed in the course of carbon monoxyde myelinopathy.

Hemorrhagic white matter infarction in three critically ill patients

Extensive areas of hemorrhagic softening developed in the cerebral white matter in three critically ill patients. The anatomic peculiarities of the vasculature of this region, as well as the possible roles of edema and vasospasm, are weighed as factors in the pathogenesis of these unusual lesions.