Intracranial Infection

a Tuberculosis a Tuberculosis

Invasive Apergillosis

c Invasive aspergillosis

Fig. 11.20a The T2-weighted sequence (left) reveals a tuberculous abscess in the right parietal lobe that is surrounded by extensive edema. In the contrast-enhanced T1-weighted sequence (right), the typical accumulation of contrast in the abscess wall is very well appreciated. b Multiple small contrast-enhancing lesions are visible in white matter and subependy-mally (around the ventricle). Some of them show ringlike structure. This cerebral toxoplasmosis developed in a patient with HIV infection. Based on imaging alone, HIV-associated lymphoma is a possible differential diagnosis. c This neutropenic patient with b Toxoplasmosis b Toxoplasmosis

d Subdural empyema c Invasive aspergillosis

Intracranial Aspergillosis

Fig. 11.20a The T2-weighted sequence (left) reveals a tuberculous abscess in the right parietal lobe that is surrounded by extensive edema. In the contrast-enhanced T1-weighted sequence (right), the typical accumulation of contrast in the abscess wall is very well appreciated. b Multiple small contrast-enhancing lesions are visible in white matter and subependy-mally (around the ventricle). Some of them show ringlike structure. This cerebral toxoplasmosis developed in a patient with HIV infection. Based on imaging alone, HIV-associated lymphoma is a possible differential diagnosis. c This neutropenic patient with d Subdural empyema

an acute myeloid leukemia has developed a mycotic abscess in the left occipital lobe with no perilesional reaction to speak of even after contrast administration (left). Only two weeks later (right), after the blood marrow has recovered, the patient is able to mount a more vigorous immune response and the same sequence reveals contrast accumulation in the abscess wall as well as along the adjacent meninges (arrows). d This chronic subdural hematoma has become infected after a primary and ineffective drainage. After contrast administration, the surrounding leptomeninges enhance significantly.

Brain abscess: A brain abscess develops after the hemato-genous spread of septic emboli to the brain (for example, in patients with endocarditis), in immunosuppressed patients, and with direct or venous intracranial spread of bacteria stemming from infected paranasal sinuses (see Fig. 13.7d, p. 290) or the mastoid air cells. In an immuno-competent patient, a brain abscess typically shows strong contrast enhancement in the periphery of the lesion and extensive surrounding edema (Fig. 11.20a).

Advanced HIV infection, therapeutic immunosuppression after solid organ transplantation, advanced hematological diseases, and aggressive chemotherapy can significantly impair the immune response of a patient and dissemi nated fungal abscesses may develop (Fig. 11.20b, c). These fungal lesions often fail to exhibit the strongly contrast-enhancing abscess membranes that reflect the intact normal immune response in the common bacterial infections. Of course, hematomas can also become superinfected (Fig. 11.20d).

Lymphoma: Two percent of all brain tumors are lymphomas. These are particularly frequent in HIV-infected patients. Lymphomas enhance significantly after contrast administration. Morphologically it may be challenging to differentiate them from a glioblastoma or an abscess (Fig. 11.21).

I Intracranial Lymphoma

I Intracranial Lymphoma

Intracerebral Lymphoma
Fig. 11.21 In this patient, lymphoma involves the basal ganglia and insinuates itself around the ventricle. Such findings in an HIV patient are difficult to differentiate from toxoplasmosis on morphological grounds. Correlation with laboratory findings helps.

Multiple sclerosis (MS): Multiple sclerosis is a demyelinat-ing disease of early adulthood and of unknown etiology. It may run an acute relapsing or a continuously progressive course. The symptomatology is quite variable, which is why brain tumors must also be excluded as a cause when nonspecific neurological symptoms are encountered. The demyelinated lesions are typically located in the immediate vicinity of the lateral ventricle and are oriented in a centrifugal pattern. In active disease the lesions may accumulate contrast (Fig. 11.22). MS is generally diagnosed by CSF analysis.

• Diagnosis: Paul diagnoses a solitary, aggressive, intraaxial primary brain tumor—most likely a glioblastoma. Gregory has to agree: an inflammatory process seems very unlikely on the basis of the patient history. The neurosurgical biopsy performed a few days later unfortunately confirms the suspected tumor type. The Lee-Chongs need a lot of strength now to deal with the dire consequences of this devastating diagnosis.

f Brain tumors very rarely metastasize to extracranial loca-i tions, but quite a few extracranial tumors metastasize into the head.

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