Focal lesions

Progressive multifocal leukoencephalopathy (PML) is historically a rare demyelinating disease that is usually associated with disorders of the reticuloendothelial system, neoplasias and immunosuppressive therapy [1, 2]. However, it has become more important in clinical medicine because it is frequently seen as an opportunistic secondary infection in immunocompromised persons with AIDS. PML is characterized by focal lesions that are noninflammatory and caused by infection of oligodendrocytes with the JC papovavirus. 

Dystonia due to identifiable structural or biochemical abnormalities ( secondary dystonia) often occurs weeks or months after strokes or other focal lesions, which commonly involve the basal ganglia, but may also involve the thalamus or cerebellum. Dystonia is also seen in children with cerebral palsy and in patients with abnormalities of dopaminergic transmission. For instance, dystonia may develop in the context of Parkinson s disease, either as an early parkinsonian sign, or in response to dopaminergic drugs. A particularly interesting inherited disease results in a combination of dystonia and parkinsonian features at a young age, which responds dramatically to treatment with low-dose levodopa ( dopamine-responsive dystonia ). 

Sugarbaker P, Vermess M, Doppman J, Miller D, Simon R (1984) Improved detection of focal lesions with computerized tomographic examination of the liver using ethiodized oU emulsion (EOE-13) liver contrast. Cancer 54 1489... 

Seizures ( rum fits ), which are generalized motor events that usually peak 12 to 48 hours after cessation of alcohol consumption. Partial seizures suggest a focal lesion and require careful neurological evaluation. 

Fig. 9.2. Fluid-attenuated inversion recovery (FLAIR, upper row) and T2-weighted (lower row) magnetic resonance images demonstrating early small focal lesions of leukoaraiosis...

Fig. 9.7a-f. White matter changes in regions other than the periventricular area (FLAIR images), a Multiple small focal lesions, b Multiple large focal lesions, c Multiple focal confluent lesions, d Diffusely confluent lesions irregular in shape. e,f Extensive... 

Small focal lesions < 5 mm, mostly rounded Large focal lesions 6-10 mm, mostly rounded... 

Focal confluent lesions 11-25 mm, various shapes, may have irregular borders Diffusely confluent lesions >25 mm, mostly with irregular borders Extensive white matter change diffuse hyperintensity without focal lesions... 

Fig. 9.9. FLAIR (left) and T2-weighted (middle) images, and apparent diffusion coefficient (ADC) map (right) of a patient with leukoaraiosis. Multiple small and large focal lesions can be detected better on the FLAIR image than on the T2-weighted image. Lesions appear hyperintense (bright) on the ADC map indicating increased diffusion...

Renal 0.8 2.9 (micoscopic focal lesions in renal tubular ... 

Haemangioma (see chapter 36.4.4) - the most common benign finding - is usually detected incidentally as a homogeneous and frequently circular focal lesion. It is... 

The sensitivity of CT for the confirmation of focal lesions is 84-96%, with a specificity of 86-100%. Differentiation between intra- and extrahepatic obstruction was successful in 77-97% of cases the location of the obstruction was clarified in 79-98%, and the aetiology of the obstruction was established in up to 76% of cases. 

Benign focal lesions usually lead to a smoothly curved displacement of arteries (and veins). In the parenchymal phase, they show more or less sharply delineated filling defects. (132, 145, 156)... 

The great value of nuclear medical examinations lies in the fact that the test results (including those produced by static scans) reflect biological functions. Furthermore, such methods can help to define the benignancy/malignancy and structural origin of the respective focal lesion. 

Focal lesions with a diameter of > 1.5 cm can be detected with a sensitivity of >80% and are visible as circumscribed storage defects, e.g. in the case of amoebic ab-... 

Computer tomography can be indicated in isolated cases, particularly in order to establish the cause of obstruction or when focal lesions are present. 

Benign hepatic focal lesions are usually detected as an incidental finding in sonography. As a rule, there are no subjective or characteristic complaints, no identified neoplastic disease and no objective clinical findings. 

Tab. 36.1 Sonomorphological classihcation of benign hepatic focal lesions according to their (predominant) echogenicity...

Tab. 36.3 Respective values of the different diagnostic methods regarding the detection of hepatic focal lesions (US = ultrasound, CT = computer tomography, MRI = magnetic resonance imaging, SC = scintigraphy, FNB = fine-needle biopsy. Lap = laparoscopic findings at the liver surface)...

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