Toxoplasma encephalitis in Haitian adults with acquired immunodeficiency syndrome: a clinical-pathologic-CT correlation

Injection with Toxoplasma gondii protein affects neuron health and survival

Toxoplasma gondii is an intracellular parasite that causes a long-term latent infection of neurons. Using a custom MATLAB-based mapping program in combination with a mouse model that allows us to permanently mark neurons injected with parasite proteins, we found that Toxoplasma-injected neurons (TINs) are heterogeneously distributed in the brain, primarily localizing to the cortex followed by the striatum. In addition, we determined that cortical TINs are commonly (>50%) excitatory neurons (FoxP2+) and that striatal TINs are often (>65%) medium spiny neurons (MSNs) (FoxP2+). By performing single neuron patch clamping on striatal TINs and neighboring uninfected MSNs, we discovered that TINs have highly aberrant electrophysiology. As approximately 90% of TINs will die by 8 weeks post-infection, this abnormal physiology suggests that injection with Toxoplasma protein-either directly or indirectly-affects neuronal health and survival. Collectively, these data offer the first insights into which neurons interact with Toxoplasma and how these interactions alter neuron physiology in vivo.

Imaging in Differentiating Cerebral Toxoplasmosis and Primary CNS Lymphoma With Special Focus on FDG PET/CT

OBJECTIVE. The purpose of this article is to present a brief review of literature evaluating different imaging modalities with special focus on ¹⁸F-FDG PET/CT in differentiating cerebral toxoplasmosis and primary CNS lymphoma. CONCLUSION. Differentiating cerebral toxoplasmosis and primary CNS lymphoma is crucial in the care of patients with HIV infection. Delayed diagnosis can lead to considerable morbidity and mortality. The reference standard for diagnosis is biopsy and histopathologic examination. Biopsy has disadvantages due to its invasive nature and associated complications. Noninvasive imaging can be an alternative to biopsy for differentiation of toxoplasmosis and primary CNS lymphoma. Despite advances in MRI techniques, prophylaxis of opportunistic infection, and treatment of HIV infection, clinical situations continue to arise in which the diagnosis is not clear. In these instances, molecular imaging can be helpful.

Cerebral toxoplasmosis in patients with acquired immune deficiency syndrome in the neurological emergency department of a tertiary hospital

INTRODUCTION

Cerebral toxoplasmosis is the most common cause of space occupying brain lesion in patients with HIV/AIDS in Brazil. In the post-HAART era, it is responsible for high rates of morbidity and mortality worldwide.

MATERIALS AND METHODS

This study consists of a case series of 56 patients diagnosed with cerebral toxoplasmosis whose clinical features, brain imaging and cerebrospinal fluid aspects were analyzed.

RESULTS

Cerebral toxoplasmosis led to the diagnosis of infection by the human immunodeficiency virus (HIV) in 27 (48.2%) of the patients, while 29 (51.2%) others already knew to be HIV seropositive. However, at the time of diagnosis of cerebral toxoplasmosis, only 9 (16.6%) reported being under antiretroviral therapy and 5 (8.9%) were receiving primary prophylaxis for toxoplasmosis. Headache, strength deficit and fever were the most frequent signs and symptoms throughout the study. Fifty-three patients showed changes consistent with toxoplasmosis in CT or MRI. Thirty-four (60.7%) CSF samples were positive in the indirect haemagglutination test and for the reaction of Toxoplasma gondii IgG ELISA, while 31 (55.4%) were positive in the direct haemagglutination test. Fifty (89.3%) patients underwent first-line treatment for toxoplasmosis.

CONCLUSION

Cerebral toxoplasmosis is still a very relevant neurological disease in individuals with AIDS admitted to neurology emergency departments. Early diagnosis and initiation of empiric treatment and antiretroviral therapy are important for good prognosis.

Acute Confusional State: A Manifestation of Toxoplasma and CMV Co-infection in HIV Patient

Context:

When dealing with a patient with HIV that presents with an altered mental status, there are various infections and disease etiologies a physician has to rule out that may play a role in complicating the inherent complex nature of HIV. Toxoplasma gondii (T. gondii) and cytomegalovirus (CMV) affect a large part of the world's population and lead to a varied and broad symptomatology depending upon the severity of HIV, the CD4 count and how early the infection is diagnosed.

Case Report:

We report an HIV+ patient in his early 50s and with a low CD4 count that presented with severe lethargy and confusion. Imaging studies that were performed after stabilizing the patient revealed a ring-enhancing lesion in the brain and after further testing, a diagnosis of reactivated T. gondii with co-infection with CMV was made. Patients infected with T. gondii that are already immune-compromised deteriorate rapidly and the disease diagnosis poses several challenges.

Conclusion:

Clinicians have to be extremely careful about making a prompt diagnosis and initiate treatment without delay before the infection takes a deadly toll on the patient. Since our patient was not on the required prophylactic medication to prevent infection with T. gondii, it was imperative to start treatment in a timely manner and to monitor the patient for any further decline in functioning.

The distribution of Toxoplasma gondii cysts in the brain of a mouse with latent toxoplasmosis: implications for the behavioral manipulation hypothesis

Background

The highly prevalent parasite Toxoplasma gondii reportedly manipulates rodent behavior to enhance the likelihood of transmission to its definitive cat host. The proximate mechanisms underlying this adaptive manipulation remain largely unclear, though a growing body of evidence suggests that the parasite-entrained dysregulation of dopamine metabolism plays a central role. Paradoxically, the distribution of the parasite in the brain has received only scant attention.

Methodology/Principal Findings

The distributions of T. gondii cysts and histopathological lesions in the brains of CD1 mice with latent toxoplasmosis were analyzed using standard histological techniques. Mice were infected per orally with 10 tissue cysts of the avirulent HIF strain of T. gondii at six months of age and examined 18 weeks later. The cysts were distributed throughout the brain and selective tropism of the parasite toward a particular functional system was not observed. Importantly, the cysts were not preferentially associated with the dopaminergic system and absent from the hypothalamic defensive system. The striking interindividual differences in the total parasite load and cyst distribution indicate a probabilistic nature of brain infestation. Still, some brain regions were consistently more infected than others. These included the olfactory bulb, the entorhinal, somatosensory, motor and orbital, frontal association and visual cortices, and, importantly, the hippocampus and the amygdala. By contrast, a consistently low incidence of tissue cysts was recorded in the cerebellum, the pontine nuclei, the caudate putamen and virtually all compact masses of myelinated axons. Numerous perivascular and leptomeningeal infiltrations of inflammatory cells were observed, but they were not associated with intracellular cysts.

Conclusion/Significance

The observed pattern of T. gondii distribution stems from uneven brain colonization during acute infection and explains numerous behavioral abnormalities observed in the chronically infected rodents. Thus, the parasite can effectively change behavioral phenotype of infected hosts despite the absence of well targeted tropism.

Pathology of tropical diseases

Tropical diseases affecting the central nervous system include infections, infestations, and nutritional deficiency disorders. This article discusses the commonly encountered diseases. The infections include bacterial, mycobacterial, fungal, parasitic, and viral infections with varied clinical manifestations. Imaging sensitivity and specificity for the prediction of the cause of infections has improved with application of advanced techniques. Microbial demonstration and histology remain the gold standard for diagnosis. Understanding the basis of imaging changes is mandatory for better evaluation of images. Nutritional disorders present with generalized and nonspecific imaging manifestations. The pathology of commonly encountered vitamin deficiencies is also discussed.

Emergent neuroimaging of intracranial infection/inflammation

Infectious and inflammatory processes of the intracranial compartment often result in acute clinical presentations. The possible causes are legion. Clues to the diagnosis involve clinical presentation, laboratory analysis, and neuroimaging. This article reviews some of the salient factors in understanding intracranial infection/ inflammation, including pathophysiology and neuroimaging protocols/findings, and provides some examples and a few "pearls and pitfalls."

HIV and the central nervous system

Neurological complications of HIV infection are common with clinically recognized disorders ultimately affecting between 40% and 75% of patients. The spectrum of neurological disease is broad. This article highlights the common disorders of the central nervous system associated with HIV/AIDS.

Toxoplasma infection in systemic lupus erythematosus mimicking lupus cerebritis

An opportunistic infection is a known, although under-diagnosed, complication of systemic lupus erythematosus (SLE). A 48-year-old woman with a recent diagnosis of SLE was admitted to the hospital because of a fever, confused state, and convulsive episode. Her symptoms were interpreted as being compatible with lupus cerebritis. Treatment with methylprednisolone resulted in a temporary improvement in the patient's condition. Nevertheless, during the next few weeks, her physical and mental condition deteriorated, and she died of massive pulmonary emboli. An autopsy revealed no signs of lupus cerebritis; however, disseminated cerebral toxoplasmosis was found. Cerebral toxoplasmosis is a rare complication of SLE that may be misdiagnosed as lupus cerebritis.

[Toxoplasmic and chagasic meningoencephalitis in patients with human immunodeficiency virus infection: anatomopathologic and tomographic differential diagnosis]

Twenty-two HIV+ patients with encephalitis were studied. Of these, 7 had meningoencephalitis due to Toxoplasma gondii (MT) and 15 due to Trypanosoma cruzi (MC). Pathologic and computerized axial tomography (CAT) changes were compared. We found that focal necrotizing encephalitis due to Toxoplasma involved the cerebral cortex and the basal ganglia, whereas lesions due to Trypanosoma cruzi were centered in the white matter, sometimes extending into the cortex. Hemorrhages, myelin lesions and organisms were more pronounced in chagasic than in toxoplasmic encephalitis. These findings are consistent with the literature reviewed.

Chagasic meningoencephalitis in the immunodeficient

Based on their own experience and on the literature, the authors compare the brain pathology due to HIV+ associated Trypanosoma cruzi reactivated infection to that described for the natural history of the Chagas' disease (CD). The peculiar focal necrotizing chagasic meningoencephalitis (MECNF) which appears only in immunedeficient chagasics, especially when the deficiency is due HIV is a safe criterion for reactivation of CD. MECNF morphologic findings are unlike to those found either for some cases of acute phase CD or for chronic nervous form of CD.

Focal brain lesions in patients with AIDS: aetiologies and corresponding radiological patterns in a prospective study

We report the results of a hospital-based study of 188 consecutive patients seropositive for the human immune deficiency virus type 1 (HIV-1) who presented in a 4-year period (1988-1991) with possible signs or symptoms of first-ever central nervous system disease. Confirmed diagnoses were cerebral toxoplasmosis in 47 patients (25.0%), HIV-1 encephalopathy in 19 (10.1%), progressive multifocal leucoencephalopathy (PML) in 9 (4.8%), cerebral lymphoma in 1 (0.5%), and other conditions in 9 patients (4.8%). Seventy-three subjects (38.8%) showed focal brain lesions on initial computed tomography or magnetic resonance imaging, which were assessed prospectively. Positive predictivity for toxoplasmosis was 100% if multiple lesions occurred in combination with mass effect or contrast enhancement (23 patients), or if at least one space-occupying or enhancing lesion was located in the basal ganglia or the thalamus (26 patients). Solitary lesions with mass effect or contrast enhancement were seen in 26 patients and were caused by cerebral toxoplasmosis in 22 (84.6%). Eight of the 9 PML patients presented with one or more non-enhancing, non-mass lesions, although the predictive value of this pattern was low (47.1% for PML). Thus, in our epidemiological context, certain imaging findings in HIV-1-seropositive patients were highly predictive of cerebral toxoplasmosis. This may differ from findings from other parts of the world where cerebral toxoplasmosis may be less prevalent among HIV-1-infected individuals.

Pyrimethamine-clarithromycin combination for therapy of acute Toxoplasma encephalitis in patients with AIDS

Clarithromycin, a new macrolide, is effective in treating experimental Toxoplasma gondii infection. A pyrimethamine-clarithromycin combination was evaluated for the treatment of acute Toxoplasma encephalitis in 13 AIDS patients. The scheduled regimen was 2 g of clarithromycin per day and 75 mg of pyrimethamine per day for 6 weeks. The protocol was completed in eight patients and stopped in five patients (because of voluntary withdrawal by two patients, deterioration of neurological condition and thrombocytopenia in two patients, and suspicion of liver toxicity in one patient). The clinical and computed tomography scan responses at week 6 of treatment were 80 and 50%, respectively. Two patients died, one of toxoplasmic encephalitis and the other of cerebral bleeding due to pyrimethamine-induced thrombocytopenia. Adverse events related to therapy were nausea and/or vomiting (38%), skin rash (38%), significant increase of liver tests (24%), hearing loss (15%), and severe hematological abnormalities (31%). In this pilot study, a pyrimethamine-clarithromycin combination was shown to be comparable to the conventional regimen for the treatment of acute Toxoplasma encephalitis in AIDS patients.

Review of the central nervous system cytopathology in human immunodeficiency virus infection

The human immunodeficiency virus (HIV) is a neurotropic retrovirus capable of producing a wide spectrum of central nervous system changes. Nearly 40% of HIV-infected patients demonstrate neuropathy ranging from dementia to the opportunistic infections and neoplasia seen in the acquired immunodeficiency syndrome (AIDS). Dramatic increases in the numbers of AIDS cases have allowed for the cytotechnologist and cytopathologist to become acquainted with the various pathologic manifestations of HIV infection. In this review, we are reporting the HIV-related diseases in the central nervous system and the role of diagnostic cytology.

MRI evaluation of AIDS-related encephalopathy: toxoplasmosis vs. lymphoma

The spectrum of cranial MRI findings was evaluated in 113 patients with the acquired immunodeficiency syndrome, assessing lesion number, size, location, and configuration in association with the autopsy and/or biopsy results. Correlation of cranial MRI and CT was performed in 32 patients. MRI was shown to be superior in sensitivity of lesion detection demonstrating more lesions than CT in 14 studies (44%) and equivalent information in 18 studies (56%). In no case did CT demonstrate lesions not detected on MRI. We conclude that MRI should be the study of choice in evaluating AIDS-related encephalopathy. Multiple lesions that involve both deep gray matter and white matter suggest the possibility of CNS lymphoma. The "target" appearance on MRI is not helpful in distinguishing toxoplasmosis from lymphoma.

Primary cerebral lymphoma in acquired immunodeficiency syndrome (AIDS)--CT manifestations

Primary lymphoma of the brain in AIDS is being observed with increased frequency; five pathologically proven cases are presented. Although the CT patterns may correlate well with patterns previously described in lymphoma, occasionally an irregular ring-like lesion may occur which is difficult to distinguish from toxoplasmosis or other inflammatory processes without appropriate pathological material.

Circulating antigen of Toxoplasma gondii in patients with AIDS: significance of detection and structural properties

232 sera and 40 cerebrospinal fluid samples of altogether 125 patients in stages III or IV of a HIV-infection were tested for circulating antigen of Toxoplasma gondii by means of a three-layer enzyme-linked immunosorbent assay. Circulating antigen was detected in 32 sera of 20 patients (= 16% of all persons investigated). These ELISA results were reexamined by an Immunoblot following a SDS-PAGE and confirmed in most cases. In addition, this test system led to a partial characterization of the circulating antigen; it consists of at least two proteins with atomic mass units of 27 and 57 kd respectively. The antigenemia was correlated with IgG- and IgM-antibody titres, with clinical symptoms, and with pathological findings also. Our results indicate that the detection of circulating antigen in sera offers a rapid and efficient method for the diagnosis of an acute toxoplasmosis in AIDS-patients.

Treatment of central nervous system toxoplasmosis with pyrimethamine/sulfadiazine combination in 35 patients with the acquired immunodeficiency syndrome. Efficacy of long-term continuous therapy

Thirty-five patients with the acquired immunodeficiency syndrome (AIDS) and central nervous system toxoplasmosis, seen over a 30-month period, were treated with the combination pyrimethamine/sulfadiazine. All patients had clinical and computed tomographic scan findings consistent with active neurotoxoplasmosis. Mean duration of total therapy was six months. During the first two months of therapy, four patients died of acute neurotoxoplasmosis and 31 showed improvement. Of the 24 patients evaluable for long-term therapy, 14 (58 percent) achieved complete resolution and 10 had late clinical (n = 7) and/or computed tomographic scan (n = 6) sequelae. Six patients experienced 10 relapses, which occurred within six weeks of treatment discontinuation in seven of 10. Reintroduction of the combination led to complete resolution of the relapse in eight cases. These clinical results were correlated with brain anatomic findings in the 15 autopsied cases. Side effects, noted in 25 of 35, were mainly hematologic toxicity (n = 21) and cutaneous rash (n = 12). However, the combination had to be definitively stopped in only two cases and sulfadiazine alone had to be withdrawn in eight other cases. These data suggest that pyrimethamine/sulfadiazine is highly efficacious in neurotoxoplasmosis and that life-long therapy is needed to prevent relapses in patients with AIDS.

Opportunistic central nervous system pathology in patients with AIDS

Central nervous system disease related to the acquired immunodeficiency syndrome (AIDS) includes both those illnesses arising from primary human immunodeficiency virus infection and those secondary to opportunistic processes. Ten percent of AIDS patients present with neurological illness; nearly 40% have significant neurological symptoms and 75% have neuropathological abnormalities on autopsy. The frequency of multiple central nervous system pathological processes in the neurologically symptomatic AIDS patient may approach 30%, making the diagnosis and follow-up of these patients extremely difficult. Specific AIDS-related opportunistic infections of the central nervous system are discussed.

Neurological complications in AIDS

Neurological complications in the acquired immunodeficiency syndrome (AIDS) are an important aspect of this new infectious disease and occur frequently. The existence of neurotropic variants of the human immunodeficiency virus (HIV), the causative agent of AIDS, is probable. Direct infection of the nervous system with HIV leads to a variety of HIV-induced neurological syndromes, the AIDS dementia complex being its most important representative. In addition, a large number of opportunistic infections and malignancies of the nervous system may complicate the disease. Major aspects of the clinical pictures, rational diagnostic approaches and treatment options of the most important sequels of HIV infection of the nervous system are discussed.

Advantage of magnetic resonance imaging in the diagnosis of cerebral infections

18 patients with cerebral infections were investigated with a 1.5 Tesla-Magnetom. The results are compared to CT-findings obtained at the same time. In the majority of cases (n = 11) MR is superior to CT because it allows earlier detection of the disease, a more exact definition of the spread and a more detailed representation of complex inflammatory processes. MRI should rank first among all examination methods, especially in the determination of herpes simplex-encephalitis as it allows earlier detection and treatment of this disease.

Primary central nervous system lymphoma in acquired immune deficiency syndrome: a clinical and pathological study

Twenty cases of primary lymphoma of the central nervous system associated with acquired immune deficiency syndrome were seen over a period of four years and were studied clinically and pathologically. Biopsy established the diagnosis in 11 cases, and autopsy confirmed it in 9. Multicentricity was demonstrated in all cases for which there was adequate autopsy material. Both large-cell immunoblastic and small noncleaved lymphomas were seen, and marker studies in 5 patients established that the lymphomas were of B-cell origin. Neurological symptoms and signs, cerebrospinal fluid characteristics, and radiographic appearance were reviewed. The clinical and radiographic picture is nonspecific and histological confirmation is essential for diagnosis. Although the tumor appears to be radiosensitive, prognosis is extremely poor, with an average survival of less than two months.

Intracerebral mass lesions in patients affected by AIDS

"Toxoplasma gondii" cerebral abscess is a common opportunistic infection in patients affected by AIDS. Making a reliable diagnosis of acute cerebral toxoplasmosis is difficult in AIDS patients because of the lack of specificity of serological data and neuroradiological findings. Brain biopsy is the only procedure which enables a reliable diagnosis to be made a trial of specific medical therapy for toxoplasmosis in patients affected by AIDS and intracranial mass lesion can be advisable before performing brain biopsy. The authors report the cases of three patients affected by AIDS and cerebral toxoplasmosis. Tissue diagnosis was made in the first patient from autopsy material while a presumptive diagnosis was made in the other two cases since specific medical therapy resulted in a dramatic improvement of the neurological status. Despite the good possibilities in the treatment of this complication AIDS, however, carries a poor prognosis.

Cryptococcal meningitis and cerebral toxoplasmosis in a patient with acquired immune deficiency syndrome

A 34-year-old homosexual male developed cryptococcal meningitis as the initial manifestation of Acquired Immune Deficiency Syndrome (AIDS). With antifungal therapy he improved. Six weeks later he developed focal motor seizures and progressive hemiplegia. Computer assisted tomography revealed multiple, ring-enhancing, low density lesions. The patient expired and at necropsy he was found to have multiple toxoplasma brain abscesses as well as chronic cryptococcal meningitis. This case demonstrates that in a patient with AIDS with pre-existing central nervous system infection who develops new neurological symptoms the possibility of a second and potentially treatable infection must be considered and its diagnosis pursued vigorously.

Acquired immune deficiency syndrome (AIDS) and consultation-liaison psychiatry

Acquired Immune Deficiency Syndrome (AIDS) is a new highly lethal transmissible syndrome that occurs primarily in identified high-risk groups. The number of AIDS cases has been doubling approximately every 6 months in the United States since 1981. A large number of healthy HTLV-III seropositive individuals, and a significant number of individuals with AIDS-related complex (ARC), who are at increased risk for eventual development of AIDS, have been identified. At least one third of AIDS patients develop neurologic disease prior to death. Organic mental disorders are frequent in AIDS and can have devastating consequences. Severe psychologic distress and functional psychiatric syndromes are also common. The psychosocial effects of AIDS for patients, family and friends, and health-care professionals are discussed in relationship to the psychosocial consequences of other serious medical illnesses including cancer. An ideal comprehensive program to meet the needs of "AIDS affected" individuals is presented, as are the authors' views on the tasks of C-L psychiatrists in participating in the comprehensive care of these individuals.

[Toxoplasmosis of the central nervous system in a diabetic patient]

The author describes a case of a central nervous system toxoplasmosis in a diabetic patient. A review of the literature about toxoplasmosis and its predisposing causes was made, and diabetes has not been reported up till now among them.

Detection of Toxoplasma cysts and oocysts in an urban environment in a developed country

Feces of 115 stray or unwanted cats were screened for Toxoplasma oocysts by sucrose density centrifugation and inoculation into mice. None of the feces examined contained detectable levels of viable oocysts. Using a laboratory infected cat, the sensitivity of this detection technique was found to be about 250 oocysts/g of feces by microscopic analysis and about 2 oocysts by mouse inoculation. Samples of pork and lamb chops bought from suburban butcher shops were screened for Toxoplasma cysts by pepsin digestion and mouse inoculation. One of the 30 pork and none of the 30 lamb chops contained viable cysts. Experimental studies determined that the sensitivity of this method of detection was about 1 cyst/100 g of tissue. The relative likelihood of each route of Toxoplasma infection for members of an urban community in a developed country is discussed.

Neurological manifestations of the acquired immunodeficiency syndrome (AIDS): experience at UCSF and review of the literature

In this review of the acquired immunodeficiency syndrome (AIDS), the authors have evaluated a total of 352 homosexual patients with AIDS or generalized lymphadenopathy managed at the University of California, San Francisco (UCSF), between 1979 and 1984. Of an initial unselected group of 318 patients, 124 (39%) were neurologically symptomatic, and one-third already had their neurological complaints at the time of presentation. An additional 210 AIDS patients with neurological symptoms have been reported in the literature. Thus, a total of 366 neurologically symptomatic patients with AIDS or lymphadenopathy are reviewed. Central nervous system (CNS) complications, encountered in 315 patients, included the following viral syndromes: subacute encephalitis (54), atypical aseptic meningitis (21), herpes simplex encephalitis (nine), progressive multifocal leukoencephalopathy (six), viral myelitis (three), and varicella-zoster encephalitis (one). Non-viral infections were caused by Toxoplasma gondii (103), Cryptococcus neoformans (41), Candida albicans (six), Mycobacteria (six), Treponema pallidum (two), coccidioidomycosis (one), Mycobacterium tuberculosis (one), Aspergillus fumigatus (one), and Escherichia coli (one). Neoplasms included primary CNS lymphoma (15), systemic lymphoma with CNS involvement (12), and metastatic Kaposi's sarcoma (three). Cerebrovascular complications were seen in four patients with hemorrhage and five with infarction. Five patients in the UCSF series had multiple intracranial pathologies, including two cases of simultaneous Toxoplasma gondii infections and primary CNS lymphoma, two cases of coexistent Toxoplasma gondii and viral infections, and one case of combined Toxoplasma gondii and atypical mycobacterial infection. Cranial or peripheral nerve complications, seen in 51 patients, included cranial nerve syndromes secondary to chronic inflammatory polyneuropathy (five), lymphoma (five), and Bell's palsy (five). Peripheral nerve syndromes included chronic inflammatory polyneuropathy (12), distal symmetrical neuropathy (13), herpes zoster radiculitis (six), persistent myalgias (two), myopathy (two), and polymyositis (one). In light of the protean behavior of AIDS and the problems related to the clinical, radiological, and serological diagnosis of the unusual and varied associated nervous system diseases, patients with AIDS and neurological complaints require a rigorous and detailed evaluation. The authors' experience suggests that biopsy of all CNS space-occupying lesions should be performed for tissue diagnosis prior to the institution of other therapies.

The antigenic structure of Toxoplasma gondii: a review

Even though T. gondii is ubiquitous in the animal kingdom, definitive information on its antigenic structure has only become available over the last few years, largely as a result of recent advances in immunology and biochemistry. New knowledge in this area will enable the immune response to the parasite to be studied in greater detail and may lead to the development of newer, more meaningful diagnostic tests for toxoplasmosis, and possibly a vaccine against it. This paper reviews knowledge on the antigenic structure of this extremely widespread and important protozoan parasite.

Neuropathologic observations in acquired immunodeficiency syndrome (AIDS)

Neuropathologic changes are described in eight fatal cases of the acquired immunodeficiency syndrome (AIDS), including four subjects who were i.v. drug abusers (two women, two men), two Haitian men, one bisexual man, and one women who had no known risk factors for AIDS. All cases had significant infections of the brain, with examples of bacterial, fungal, protozoal, and viral disease in the group. Combined infections were observed in three cases, including one case of previously unreported central nervous system (CNS) abscess due to Nocardia (combined with Salmonella). The most frequent CNS pathogen was Toxoplasma gondii, which in both Haitian subjects co-existed with systemic tuberculosis, leading to diagnostic difficulty. Only one case of "subacute encephalitis" was represented, although in other cases microglial nodules were associated with Toxoplasma and Cryptococcus organisms, as well as probable cytomegalovirus. Non-infectious complications included a cerebral infarct (one case), central pontine myelinolysis (one case), and diffuse microcystic change of the white matter (one case).

Toxoplasmosis presenting as panhypopituitarism in a patient with the acquired immune deficiency syndrome

A 57-year-old man with a prior episode of lymphatic toxoplasmosis presented with signs of anterior panhypopituitarism, which was confirmed by standard endocrinologic evaluation. The diagnosis of central nervous system toxoplasmosis was established by brain biopsy after nondiagnostic serologic and radiographic studies. At autopsy, the anterior pituitary was necrotic, with Toxoplasma abscesses in neighboring brain structures. Clinical and laboratory data met the criteria for the acquired immune deficiency syndrome. Although this is the first reported case of toxoplasmosis presenting as panhypopituitarism, future cases may be identified since central nervous system toxoplasmosis is being recognized more frequently in patients with immunodeficiency.

Central nervous system mass lesions in the acquired immunodeficiency syndrome (AIDS)

The authors present the cases of nine patients with acquired immunodeficiency syndrome (AIDS) and intracerebral mass lesions, who were evaluated at the University of California, San Francisco, between April, 1979, and July, 1983. Eight patients were confirmed homosexual males, and none was Haitian . Their average age was 38.8 years. Tissue diagnosis was made in all patients from brain biopsy or autopsy material. Three patients initially presented for evaluation of their neurological deficits, while the other six already carried the diagnosis of AIDS at admission. Seven patients presented with multiple intracranial lesions and two had polymicrobial infection. In this series, three patients had Toxoplasma gondii brain abscesses, two had primary lymphoma, two had metastatic Kaposi's sarcoma of the central nervous system (CNS), two had focal cytomegalovirus encephalitis and one each had cryptococcal and Candida albicans brain abscesses. The clinical presentation, radiological evaluation, and serodiagnostic study of these patients were not helpful in establishing the nature of the CNS lesions. Brain biopsy is considered by the authors to be critical for the evaluation and appropriate treatment of mass lesions in patients with AIDS.

Clinical stages of human brain abscesses on serial CT scans after contrast infusion. Computerized tomographic, neuropathological, and clinical correlations

The authors describe a classification of human brain abscesses into stages of development as demonstrated on computerized tomography (CT) scans. The results of CT staging of 14 human brain abscesses are compared with the previously published findings in an experimental brain abscess model developed by the same authors. The CT criteria for categorizing brain abscesses into cerebritis and capsule stages were based on the pattern of contrast enhancement and the time-density curve of enhancement obtained from sequential CT scans after contrast infusion. Using these CT criteria, it was possible to accurately categorize all 14 brain abscesses into cerebritis and capsule stages. Histological examination of surgical and autopsy specimens provided immediate confirmation of the abscess stage in six patients. Indirect staging, based on surgical findings and/or subsequent autopsy findings, was possible in eight patients. Corticosteroid administration greatly reduced contrast enhancement in the cerebritis stage, but had little effect in the capsule stage. A systematic approach utilizing CT for establishing the diagnosis, staging, and treatment planning of brain abscess is proposed.