3. Metastasis. 4. Meningioma. 5. Partially thrombosed giant aneurysm. 6. Multiple sclerosis plaque. Answer on page 2136. CAN FA.PYIIN o.3:OTOE. 9921. CAN.
Radiology Runds
_
Michael K. McLennan, MD Thomas R. Marotta, MD Drs. McLennan and Marotta are residents in the radiology of the University of Toronto at the Toronto Hospital, Western Division.
program
Clinical History A 28-year-old single man reported the recent onset of headaches.
The most likely diagnosis is: 1. Toxoplasmosis 2. Resolving hematoma 3. Metastasis 4. Meningioma 5. Partially thrombosed giant aneurysm 6. Multiple sclerosis plaque
Answer on page 2136 CAN FA.PYIIN o.3:OTOE 9921 CAN. FAM. PHYSICIAN Vol. 35: OCTOBER 1989
2011
Answer to Radiology Rounds 1. Toxoplasmosis (in
homosexual AIDS patient) Radiologic Findings Figure 1A shows brain edema (seen as increased low density) extending from the region of the basal ganglia on the right into the white matter on the same side. Also, mass effect is noted by the shift of structures (i.e., the lateral ventricles) from right to left. After the administration of intravenous contrast (Figure 1B), a ring enhancing lesion with a low-density, non-enhancing core is seen in the right basal ganglia.
Differential Diagnosis Intraparenchymal Hemorrhage The CT appearance of an intraparenchymal hemorrhage, either de novo or within an infarct, varies, depending on its age. Subacute hemorrhage may be isodense on non-contrast CT, but becomes apparent on contrast CT because of the enhancement of the neovascular tissue surrounding the hematoma (ring enhancement).1 Edema and mass effect may also be associated, as in this case. Nonetheless, there is usually some evidence of hematoma on the non-contrast cr in the form of a localized area of increased intensity. Figure 1A has no focal area of increased intensity. Metastasis A metastatic lesion of the central nervous system may produce a ring enhancing lesion with significant edema and mass effect. The most common hematogenous metastases to the brain are from the lung, breast, kidney, colon, and skin (melanoma).2
The patient's youth makes this possibility unlikely. Meningioma Meningiomas have a hyperintense 2136
appearance on non-enhanced scans, are dural-based lesions may be intraventricular), and
cT
(some have
uniform enhancement after contrast administration. There may be associated hyperostosis of the adjacent bone. Edema is present in 30% of cases.3 Rarely, a meningioma may have irregular areas of non-enhancement, or it may be cystic in nature, giving a ring enhancing appearance.
The central location of the lesion in Figure 1 virtually eliminates meningioma as a possibility. Aneurysm A partially thrombosed giant aneurysm has a "target" appearance on enhanced CT rather than the "ring" appearance of this lesion. The target appearance occurs because the residual patent lumen of the aneurysm contains contrast. This is surrounded by a non-enhancing clot contained by the aneurysm wall. The wall may also enhance or be partly calcified. The result is alternating high-low-high concentric intensities on CT (a "target"). Multiple Sclerosis Multiple sclerosis (MS) is a disease of white matter resulting in demyelination of axons. Lesions on CT range from no abnormality to the rare finding of ring enhancing plaques with associated mass effect.4 On autopsy examination, a small percentage (4%) of MS plaques are actually found in the central gray matter.4 Although possible, it is very unlikely that this lesion is an MS plaque.
(page 2011) infections and tumors, such as primary lymphoma and Kaposi's sarcoma. Any organ system can be affected, the most common being the pulmonary, gastrointestinal, and central nervous systems. It is important for family physicians to be thoroughly aware of the various clinical and pathologic components of this deadly disease. Thirty per cent to fifty per cent of AIDS patients will develop signs or symptoms referrable to the CNS at some point during the course of their disease.5 Approximately 10% will present with CNS disorders as the first sign of AIDS.5 The CNS is involved in up to 80% of AIDS patients at autopsy.5 Focal motor and sensory symptoms, headaches and seizures suggest a focal CNS process, whereas altered level of consciousness, confusion, and meningismus suggest more diffuse pathology. The four most common patterns of CNS disease in AIDS, as demonstrated by CT and magnetic resonance imaging (MRI), are:5'6 * cerebral atrophy; * focal CNS mass lesion(s); * white matter disease; and * meningeal disease.
Discussion
Cerebral Atrophy The clinical triad of cognitive, motor, and behavioural dysfunction is known as the AIDS dementia complex.5'7 It usually indicates onset of diffuse cerebral atrophy. Most cases are caused by direct infection with HIV, the neurotropic AIDS virus, which invades brain cells directly to produce encephalitis and brain cell
The disease known as acquired immune deficiency syndrome (AIDS) has leapt from relative obscurity to the forefront of medicine during the last few years, in almost every country in the world. It is caused by the human immunodeficiency virus (HIV), which produces a defect in cell-mediated immunity and thus renders afflicted patients susceptible to opportunistic
demonstrated by CT or MRI, no biopsy is necessary, due to poor expected yield.5'7-9 Other pathogens, such as cytomegalovirus, toxoplasma, and mycobacteria, have occasionally been implicated.5'9 Treatment is limited. Focal CNs Mass Lesion Central nervous system mass lesions are present in up to 22% of AIDS
death.5'7 When such diffuse disease is
CAN. FAM. PHYSICIAN Vol. 35: OCTOBER 1989
patients with associated neurologic symptoms.10 The most common cause
Meningeal Disease The symptoms of photophobia, meningismus, headaches, and nuchal
by far is the protozoan Toxoplasma gondii,57'9 1 which is twice as common and lumbar tenderness indicate a as primary brain lymphoma.6 Less chronic meningitis process and are common causes include Candida not uncommon in AIDS. Most patients albicans, tuberculosis, Cryptococcus have nonspecific cr and MRI findings. neoformans, herpes, Kaposi's sarcoThe most common causative agent is ma, and bacterial abscesses.5 the fungus Cryptococcus Toxoplasmosis affects 10% of all neoformans.5'6'9'11 Autopsy series reAIDS patients at some point and is the veal the incidence of fungal meningimost common treatable cause of CNS tis in AIDS patients to be 5% to disease.6 Lesions are seen on cr as 15%.5,6 Diagnosis is made by rising thin walled cavities, usually multiple, cryptococcal antigen titres in the sewith low-density (necrotic) centres. rum and cerebrospinal fluid. Biopsy The capsule demonstrates enhanceis not indicated. Amphotericin B may ment on contrast cr scans (as in this control the infection, but therapy case). Many studies have promoted must be continued for the rest of the early biopsy of focal lesions,7-9'11 but patient's life. recently Federle5 suggested that patients with toxoplasmosis be treated Effectiveness of Radiology empirically with antibiotics effective The two most informative techagainst T. gondii (sulfadiazine; pyrimethamine) because it is the most niques in AIDs-related CNS disease are common cause and the other possibil- cr and MRi. In the assessment of focal ities generally have a poor prognosis. lesions, CT adequately demonstrates He recommends biopsy only if palocation, size, associated edema, and tients fail to respond to medical ther- multiplicity of lesions. Magnetic resonance imaging may reveal further apy. This antibiotic coverage, often small masses not apparent on Cr, but combined with steroids and anticonvulsants, produces rapid clinical imis recommended only if biopsy is conprovement within two weeks in most sidered and no amenable lesions are cases. The therapy must be mainnoted on the Cr scan. Post and tained indefinitely to prevent recurcolleagues8 suggest Cr alone if mulrence. tiple lesions are present. If the scan is equivocal or only a single lesion is Lymphoma is the second most common cause of focal CNS disease in demonstrated, MRI should be performed (if available). In diffuse white AIDS,5'9 occurring in about 6% of matter disease associated with propatients.6 Affected patients usually gressive encephalopathy and demendie from the disease within less than tia, the CNS disease is best demontwo months.5 strated by MRI.5'7'9 White Matter Disease Diffuse white matter disease is Summary quite common in AIDS, seen in up to 30% of cases in an autopsy series,6 alUp to half of all AIDS patients will suffer signs or symptoms of CNS inthough it is usually subclinical. The symptoms, when present, are similar volvement during the course of their to those with cerebral atrophy in the illness. Toxoplasmosis is the most freAIDS dementia complex. As with atro- quent cause of focal disease and is the most common treatable disease afphy, the most common pathogen is HIV, with cytomegalovirus, herpes, fecting the CNS in AIDS. Most cases of cerebral atrophy and diffuse white and Varicella zoster noted as other, matter disease are caused by HIV, reless common, causes.5'7'8 sulting in a poor prognosis. Progressive multifocal leukoenCryptococcus is the most common cephalopathy is another viral infection causing pathologic changes in the agent producing chronic meningitis, white matter. The etiologic agent is a which is yet another pattern in the spectrum of CNs-related disease. papovavirus known as the i-c virus.5 The patient whose X-ray films are Between 2% and 7% of AIDS patients shown had multiple CNS toxoplasmosuffer from the disorder.6 The prognosis is very poor, with rapid deterio- sis lesions. He responded well to antiration and death within four months.5 biotic treatment. x CAN. FAM. PHYSICIAN Vol. 35: OCTOBER 1989
Acknowledgements The authors thank Dr. Perry Cooper and Dr. Bob Willinsky, of the Neuroradiology Department at the Sunnybrook Medical Center, Toronto, for supplying the films and for their assistance in preparing this manuscript.
References 1. Davis JM, Hesselink JR. Vascular lesions: intracerebral hemorrhage. In: Taveras JM, Ferrucci JT, eds. Radiology: diagnosis-imaging-intervention. Vol 3. Philadelphia: JB Lippincott Co., 1988:2-4. 2. Potts DG, Albott GF, von Sneidern JV. National Cancer Institute study: evaluation of computed tomography in the diagnosis of intracranial neoplasms: III. Metastatic tumors. Radiology 1980; 136:657-64. 3. Kelly WM, Brant-Zawadzki M. Magnetic resonance imaging and computed tomography of supratentorial tumors. In: Taveras JM, Ferrucci JT, eds. Radiology: diagnosis-imaging-intervention. Vol 3. Philadelphia: JB Lippincott Co., 1988:19-21. 4. Weinstein MA, Modic MT, Charles KK. Diseases of the white matter. In: Latchaw RE, ed. Computed tomography of the head, neck and spine. Chicago: Year Book Medical Publishers, 1985:155-66. 5. Federle MP. A radiologist looks at AIDS: imaging evaluation based'on symptom complexes. Radiology 1988; 166:553-62. 6. Petito CL, Cho E-S, Lemann W, Navia BA, Price RW. Neuropathology of acquired immunodeficiency syndrome (AIDS): an autopsy review. J Neuropathol Exp Neurol 1986; 45:635-46. 7. Olsen WL, Longo FM, Mills CM, Norman D. White matter disease in AIDS: findings at MR imaging. Radiology 1988; 169:445-8. 8. Post MJD, Sheldon JJ, Hensley GT, et al. Central nervous system disease in acquired immunodeficiency syndrome: prospective correlation using cr, MR imaging and pathologic studies. Radiology 1986; 158:141-8. 9. Post MJD, Kursunoglu SJ, Hensley GT, Chan JC, Moskowitz LB, Hoffman TA. Cranial cr in acquired immunodeficiency syndrome: spectrum of diseases and optimal contrast enhancement technique. AJNR 1985; 6:743-54. 10. Levy RM, Rosenbloom S, Perrett LV. Neuroradiologic findings in AIDS: a review of 200 cases. AJR 1986; 147:
977-83.
11. Whelan MA, Kricheff II, Handler M, et al. Acquired immunodeficiency syndrome: cerebral computed tomographic
manifestations. 149:477-84.
Radiology
1983; 2137
