Vacuolar myelopathy in AIDS. A morphological analysis

Review of the neurological aspects of HIV infection

There are almost 40 million people in the world who live with the human immunodeficiency virus (HIV). The neurological manifestations associated with HIV contribute to significant morbidity and mortality despite the advances made with anti-retroviral therapy (ART). This review presents an approach to classification of neurological disorders in HIV, differentiating diseases due to the virus itself and those due to opportunistic infection. The effects of antiretroviral therapy are also discussed. The emphasis is on the developing world where advanced complications of HIV itself and infections such as tuberculosis (TB), toxoplasmosis and cryptococcal meningitis remain prevalent.

HIV-associated neurocognitive disorder and HIV-associated myelopathy in a patient with a preserved CD4, but high viral load-a rarely reported phenomenon: a case report and literature review

BACKGROUND

Despite widespread use of combination antiretroviral therapy (cART), HIV-associated neurocognitive disorder (HAND) and HIV-associated myelopathy (HAM) are not showing significant reduction in there occurrence. The HAM is a progressive myelopathy that often occur synchronously with severe form of the HAND in patients' having advanced immunosuppression. However, co-existence of less severe form of the HAND and HAM in patient with relatively preserved CD4 cells is rarely reported clinical entity in post cART era.

CASE PRESENTATION

We report a 16-year old male, acquired HIV infection vertically, was on second line regimen because of virological failure since 3 years. His current CD4 lymphocyte count is 835 cells/uL with viral RNA level of 33,008 copies/mL. Currently presented with progressive forgetfulness, gait imbalance, and a frequent staring episodes without loss of postural tone. Neurological examination was pertinent for cognitive dysfunction with score of 6 on International HIV Dementia Scale (motor speed = 3, psychomotor speed = 2, and memory recall = 1). Lower limbs power is 4^-/5, increased deep tendon reflexes, and unsteady gait. Brain MRI revealed diffuse both cortical and white matter T2 and FLAIR hyperintense lesions. Thoracic MRI showed abnormal T2 signal prolongation spanning from mid thoracic cord to conus. Electroencephalography study showed severe generalized slowing with evidence of focal dysrhythmia in bilateral frontotemporal regions. Unremarkable serum vitamin B 12 level (286 ng/mL). Virological failure with the HAND, HAM and seizure was considered. Dolutegravir +3TC + ATV/r regimen and valproate for seizure disorder was started. On 6 months follow up evaluation, he is clinically stable with significant improvement of his symptoms related to seizure disorders and modest improvement of his cognitive dysfunction, as he is now attending his school regularly. However, less improvement was observed reading his gait abnormality.

CONCLUSION

This case supports the current understanding regarding the persistent occurrence of HIV-associated neurocognitive disorder and HIV-associated myelopathy even decades after introduction of cART. Therefore, it's important to screen HIV+ patients for the HAND and HAM even if they have relatively preserved immunity. Because patient can be easily shifted to ART drugs with better CNS penetrating potential to achieve acceptable virological suppression level, to observe sound clinical improvement.

HIV-Associated Vacuolar Encephalomyelopathy

We report a case of human immunodeficiency virus (HIV)-associated vacuolar encephalomyelopathy with progressive central nervous system dysfunction and corresponding vacuolar degeneration of the spinal cord, cranial nerves, and brain, the anatomic extent of which has not previously been described.

Diffusion tensor MR imaging (DTI) metrics in the cervical spinal cord in asymptomatic HIV-positive patients

INTRODUCTION

This study was conducted to compare diffusion tensor MR imaging (DTI) metrics of the cervical spinal cord in asymptomatic human immunodeficiency virus (HIV)-positive patients with those measured in healthy volunteers, and to assess whether DTI is a valuable diagnostic tool in the early detection of HIV-associated myelopathy (HIVM).

METHODS

MR imaging of the cervical spinal cord was performed in 20 asymptomatic HIV-positive patients and in 20 healthy volunteers on a 3-T MR scanner. Average fractional anisotropy (FA), mean diffusivity (MD), and major (E1) and minor (E2, E3) eigenvalues were calculated within regions of interest (ROIs) at the C2/3 level (central and bilateral anterior, lateral and posterior white matter).

RESULTS

Statistical analysis showed significant differences with regard to mean E3 values between patients and controls (p = 0.045; mixed-model analysis of variance (ANOVA) test). Mean FA was lower, and mean MD, mean E1, and mean E2 were higher in each measured ROI in patients compared to controls, but these differences were not statistically significant.

CONCLUSION

Asymptomatic HIV-positive patients demonstrate only subtle changes in DTI metrics measured in the cervical spinal cord compared to healthy volunteers that currently do not support using DTI as a diagnostic tool for the early detection of HIVM.

Diffusion-weighted imaging, diffusion-tensor imaging, and fiber tractography of the spinal cord

In the brain, diffusion-weighted imaging (DWI) is an established and reliable method for the characterization of neurologic lesions. Although the diagnostic value of DWI in the early detection of ischemia has not diminished with time, many new clinical applications of DWI have also emerged. Diffusion-tensor imaging and fiber tractography have more recently been developed and optimized, allowing quantification of the magnitude and direction of diffusion along three principal eigenvectors. Diffusion-tensor imaging and fiber tractography are proving to be useful in clinical neuroradiology practice, with application to several categories of disease, and to be a powerful research tool. This article describes some of the applications of DWI and diffusion-tensor imaging in the evaluation of the diseases of the spinal cord.

Pilot study of intravenous immunoglobulin in HIV-associated myelopathy

There is no effective treatment for HIV-associated myelopathy (HIVM). The introduction of highly active antiretroviral therapy (HAART) has made little difference to its natural history. Spinal cord pathology reveals vacuolization and inflammation. Intravenous immunoglobulin (IVIg) is used successfully in a number of inflammatory conditions associated with HIV. In view of the potential for reversibility of the inflammatory response in HIVM, we treated 17 patients with IVIg twice over a 56-day study period. There was improvement in composite Medical Research Council (MRC) strength scores 28 days following the first infusion (increase in score: 3.94; p = 0.021). The second infusion did not produce further improvement, however there was little reduction from peak strength. These pilot data suggest that further investigation of the use of IVIg in HIVM is warranted.

Neuropathologic contributions to understanding AIDS and the central nervous system

This historical review describes the evolution of the pathogenetic concepts associated with infection by the Human Immunodeficiency Virus (HIV), with emphasis on the pathology of the nervous system. Although the first descriptions of damage to the nervous system in the acquired immunodeficiency syndrome (AIDS) only appeared in 1982, the dramatic diffusion of the epidemic worldwide and the invariably rapidly fatal outcome of the disease, before the introduction of efficient treatment, generated from the beginning an enormous amount of research with rethinking on a number of pathogenetic concepts. Less than 25 years after the first autopsy series of AIDS patients were published and the virus responsible for AIDS was identified, satisfactory definition and classification of a number of neuropathological complications of HIV infection have been established, leading to accurate clinical radiological and biological diagnosis of the main neurological complications of the disease, which remain a major cause of disability and death in AIDS patients. Clinical and experimental studies have provided essential insight into the pathogenesis of CNS lesions and natural history of the disease. The relatively recent introduction of highly active antiretroviral therapy (HAART) in 1995-1996 has dramatically improved the course and prognosis of HIV disease. However, there remain a number of unsolved pathogenetic issues, the most puzzling of which remains the precise mechanism of neuronal damage underlying the specific HIV-related cognitive disorders (HIV dementia). In addition, although HAART has changed the course of neurological complications of HIV infection, new issues have emerged such as the lack of improvement or even paradoxical deterioration of the neurological status in treated patients. Interpretation of these latter data remains largely speculative partly because of the small number of neuropathological studies related to the beneficial consequence of this treatment.

Spinal cord pathology and viral burden in homosexuals and drug users with AIDS

Unless treated with effective antiretroviral therapy many AIDS patients develop a characteristic vacuolar myelopathy of the spinal cord associated with moderate clinical disability. Opinion is divided as to whether vacuolar myelopathy is causally linked to HIV myelitis. To investigate this further, spinal cord pathology was assessed in 41 drug users, 33 homosexual men and 16 other patients, all with AIDS. Previous work has shown that HIV encephalitis is more common in Edinburgh drug users than in homosexual men. In the present study HIV myelitis (10% overall) was more common in drug users (17%) than in homosexual men (3%) (P = 0.05), whereas the incidence of opportunistic infections (7% v. 9%) and lymphomas (2% v. 6%) was comparable in the two groups, but with a slight trend in the reverse direction, reflecting similar findings in the brain. However, moderate or severe vacuolar myelopathy was equally represented in both groups (20% of drug users and 21% of homosexual men). The HIV proviral load, assessed by polymerase chain reaction in frozen samples of thoracic spinal cord in 37 cases, correlated closely with the presence of giant cells and/or with immunocytochemical evidence of productive HIV infection. In 13 cases, the proviral load was measured in cervical, thoracic and lumbar samples and proved to be uniformly high or low in individual cases. This study provides no evidence for direct involvement of HIV, cytomegalovirus, papovavirus or human foamy virus in the pathogenesis of vacuolar myelopathy.

AIDS-associated vacuolar myelopathy

AIDS-associated vacuolar myelopathy (VM) is a common neurologic complication of AIDS. Pathologically, VM is characterized by vacuolization in the lateral and posterior columns of the thoracic spinal cord and has a striking similarity with the myelopathy of vitamin B12 deficiency. In autopsy series, 20% to 55% of patients with AIDS have evidence of spinal cord disease consistent with VM. The myelopathy usually manifests late in the course of HIV infection, with slowly progressive weakness of the lower extremities, gait disorder, sensory abnormalities in the legs, impotence in men, and urinary frequency and urgency. Its course is invariably progressive and leads to severe paralysis of the lower limbs, with loss of the ability to walk and of sphincter control. The differential diagnosis is extensive and includes metabolic, infective, and neoplastic spinal cord diseases. The diagnosis is based on the clinical observation and the exclusion of other causes of myelopathy via serologic, radiographic, and cerebrospinal fluid studies. The pathogenesis of VM is unknown. Attempts to detect HIV in the spinal cord have not yielded significant results, and there is no evidence of a relationship between the presence of HIV and the development of myelopathy. A metabolic disorder of the vitamin B12-dependent transmethylation pathway, induced by HIV or cytokine activation, is considered the possible cause of VM associated with AIDS. There is no known treatment for AIDS myelopathy and there is no evidence that antiretroviral drugs can improve the symptoms or slow the progression of VM. The symptomatic treatment includes antispasticity agents, management of sphincter dysfunction, and physical therapy. Experimental treatments are being tested in clinical trials.

Vacuolar myelopathy in transgenic mice expressing human immunodeficiency virus type 1 proteins under the regulation of the myelin basic protein gene promoter

Vacuolar myelopathy is a common neurological complication in AIDS patients. The pathogenesis of this spinal cord white matter disease remains unclear and it is still debated whether infection of spinal cord with the human immunodeficiency virus type 1 (HIV-1) is causing the disease. We have generated transgenic mice expressing the entire HIV-1 genome under the regulation of an oligodendrocyte-specific promoter. These mice develop spinal cord vacuolar lesions similar to those found in AIDS patients. This animal model provides in vivo evidence linking the expression of HIV-1 proteins in oligodendrocytes to the spinal cord damage found in vacuolar myelopathy.

AIDS-associated vacuolar myelopathy and tumor necrosis factor-alpha (TNF alpha)

The spinal cords from 15 patients with AIDS-associated vacuolar myelopathy (VM), 4 AIDS patients without VM, and 5 HIV-seronegative controls, were studied with immunocytochemistry for TNF alpha. CSF and blood from HIV-seropositive patients with VM (n = 16), non-vacuolar myelopathies (n = 8), CNS infection but no clinical myelopathy (n = 31), no clinical or radiological evidence of CNS disease (n = 9), and from 7 HIV-seronegative controls with motor neurone disease were assayed for TNF alpha using an ELISA technique. TNF alpha was present on immunostaining in all the 15 cords with VM studied. The stained cells were macrophages, microglia and endothelial cells. The amount of immunostaining was higher in cords with VM compared with cords from HIV-seropositive patients without VM (p = 0.001). The distribution of staining corresponded to the areas of pathology but did not correlate with the severity of the VM. Immunostaining was also higher in the HIV-seropositive group compared to the HIV-seronegative controls (p = 0.001). There was no significant difference in the levels of TNF alpha in the CSF of patients with VM compared to any of the other groups studied. Blood levels of TNF alpha were lower in the HIV-seropositive controls without CNS disease and in the HIV-seronegative MND controls, than in patients with VM, non-vacuolar myelopathies, and CNS disease. CSF TNF alpha levels did not appear to be a reliable indicator of intramedullary levels. The findings support the hypothesis that TNF alpha may be relevant in the pathogenesis of vacuolar change in VM.

Neuroepidemiology of HIV infection

There are a variety of HIV-related neurologic complications that have numerous causes. HIV-related neurologic illnesses are specific to the stage of HIV infection, although the greatest burden of neurologic disease and the most disabling syndromes occur in the more advanced stages. As the number of HIV-infected persons continues to increase worldwide and as antiretroviral and other anti-infective therapies improve patient survival in the advanced stages of HIV infection, the burden of neurologic disease will continue to increase.

Spinal tract pathology in AIDS: postmortem MRI correlation with neuropathology

Vacuolar myelopathy (VM) and tract pallor are poorly understood spinal tract abnormalities in patients with the acquired immunodeficiency syndrome (AIDS). We studied the ability of magnetic resonance imaging (MRI) to detect these changes in spinal cord specimens postmortem and whether criteria could be formulated which would allow these conditions to be differentiated from other lesions of the spinal cord in AIDS, such as lymphoma, cytomegalovirus (CMV) and human immunodeficiency virus (HIV) myelitis. We imaged 38 postmortem specimens of spinal cord. The MRI studies were interpreted blind. The specimens included cases of VM myelin pallor, CMV myeloradiculitis, HIV myelitis, lymphoma as well as normal cords, both HIV+ve and HIV-ve. MRI showed abnormal signal, suggestive of tract pathology, in 10 of the 14 cases with histopathological evidence of tract changes. The findings in VM and tract pallor on proton-density and T2-weighted MRI were increased signal from the affected white-matter tracts, present on multiple contiguous slices and symmetrical in most cases. The pattern was sufficiently distinct to differentiate spinal tract pathology from other spinal cord lesions in AIDS.

Cytomegalovirus myelitis in perinatally acquired HIV

A 7 year old child perinatally infected with HIV who died from progressive muscular paralysis and central nervous respiratory failure is described. Cytomegalovirus (CMV) prophylaxis with a special intravenous CMV hyper-immunoglobulin had been successfully conducted for more than four years. Macroscopic and microscopic immunohistochemical examination of the spinal cord revealed a diffuse CMV infiltration of the entire myelon. CMV infected cells were identified as astrocytes, oligodendrocytes, neurons, macrophages, ependymal, endothelial, and Schwann cells. Other organs had no signs of CMV infection. Central nervous spinal CMV infection was most probably due to insufficient penetration of the blood-brain barrier by the CMV hyper-immunoglobulin. In suspicious cases early spinal magnetic resonance imaging (1.5 tesla) combined with an examination of urine and cerebrospinal fluid for CMV is recommended.

AIDS-myelopathy. A neuropathological study

Vacuolar myelopathy belongs to the AIDS-associated diseases. It is characterized by vacuolation and infiltration of the long tracts of the spinal cord by macrophages. The clinical and morphological findings of 8 AIDS-patients with vacuolar myelopathy are reported here. The syndrome developed during the final stages of AIDS and was associated with HIV-encephalopathy in 5 cases. The vacuoles were mainly due to intramyelinic swelling and vacuolation. Vacuolated macrophages and axons contributed only to a minor degree. In one case only, HIV-antigens were detected immunohistochemically. The results are discussed in the light of modern pathogenetical concepts of HIV-related diseases.

Neuropathology of the spinal cord in the acquired immunodeficiency syndrome

The neuropathologic findings in the spinal cord were reviewed in 138 consecutive autopsies of patients with the acquired immunodeficiency syndrome. In all cases both the brain and spinal cord were examined by conventional histologic techniques, and in 63 cases immunohistochemistry was used to detect human immunodeficiency virus (HIV), Toxoplasma gondii, cytomegalovirus, and JC papovavirus antigens. The most common observation was a normal spinal cord (60%). Vacuolar myelopathy (VM) was observed in 23 (17%) cases. Human immunodeficiency virus myelitis was evident in 8% of cases. Human immunodeficiency virus myelitis was associated with HIV encephalitis in 65% of the cases. Opportunistic infections of the spinal cord were uncommon, consisting of cryptococcosis (five cases), cytomegalovirus (four cases), toxoplasmosis (one case), and progressive multifocal leukoencephalopathy (one case), and almost always were seen with cerebral and/or systemic infection by these agents. Malignant lymphoma rarely involved the spinal cord (four cases); all were B-cell lymphomas and were associated with cerebral and/or systemic lymphoma. Other abnormalities rarely observed were Wallerian degeneration of the corticospinal tracts or posterior columns (6%) and focal microinfarcts. Most cases of VM (78%) were not associated with HIV myelitis, and in the five patients with both VM and HIV myelitis, HIV-infected cells were not found in the regions affected by VM. In contrast, 65% of cases with VM were associated with HIV encephalitis. The pathogenesis of VM remains unknown; it is probably not due to direct infection by HIV.

Neuropathology of human immunodeficiency virus infection

Neuropathology has defined novel HIV-specific diseases at tissue level: HIV encephalitis and HIV leukoencephalopathy. Both occur usually in the later stages of the AIDS infection and consistently demonstrate large amounts of HIV products. In contrast to this HIV-specific neuropathology, HIV-associated neuropathology features unspecific syndromes with disputed relation to HIV infection: myelin pallor, vacuolar myelopathy, vacuolar leukoencephalopathy, lymphocytic meningitis, and diffuse poliodystrophy. All types of neuropathology may contribute to clinical manifestation according to severity, extent, and distribution of lesions, but clinico-pathologic correlation may be poor in the individual case. Neuropathologic and other data suggest two major pathogenetic pathways of HIV-associated CNS damage: First, systemic and local increase of the virus load leads to HIV encephalitis or HIV leukoencephalopathy; this is corroborated by prominent HIV production within such lesions. Second, neuronotoxicity by HIV proteins or factors secreted from infected cells is supported by histological changes of diffuse poliodystrophy and by morphometric loss of frontocortical neurons.