Introduction Section 1 Section 2 Section 3 Conclusion and References


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Section 1 - Direct leukemic involvement of the Central Nervous System

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Meningeal disease: Leukemic infiltration of the meninges

The manner in which leukemic cells enter the CNS is a subject of controversy, but the likely sources include hematogenous spread or direct spread from adjacent infiltrated bone marrow. Meningeal involvement is more common in the acute leukemias (ALL and AML) and may occur as part of the original presentation. More commonly however, meningeal spread occurs in the form of relapse after initial remission, despite aggressive anti-CNS prophylaxis. In addition to the morbidity and mortality associated with CNS relapse, the greatest risk is the invariable development of bone marrow/systemic recurrence which follows CNS relapse. Table 2 lists the signs and symptoms of leukemic meningitis, the most common form of CNS spread or meningeal form of leukemia. Leukemic meningitis may be diffuse (case 1 and case 2), or focal (case 3).


The diagnosis of leukemic meningitis generally depends on the detection of leukemic cells in the CSF, however cytology can be falsely negative. Imaging may be necessary. Findings include hydrocephalus (may be the only finding), or an abnormal MR appearance of CSF on precontrast imaging. If CSF is not of appropriate signal intensity on T1 and T2-weighted images, the possibility of leukemic meningitis should be raised. Abnormal meningeal enhancement, in the cisterns or along the pial surface of the brain or spinal cord, is the surest sign of leukemic meningitis (cases 1-3). This may be smooth or nodular. MRI is known to be far more sensitive in the detection of leptomeningeal tumor spread than CT, however CT can make this diagnosis in flagrant cases. Be aware that this type of enhancement is nonspecific (see pitfalls). Dural spread of leukemia is best detected radiologically as abnormally thickened and brightly enhancing dura on Gd-enhanced MRI.


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