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Although GBM has been reported in patients of all age groups, it is most common in late adulthood, with a peak prevalence between 65 and 75 years of age (5). There is a very slight male predilection for GBM (1.6:1) (6), and it occurs more commonly in whites than in persons of African, Asian, or Latin American descent (7).
The clinical presentation of a patient with a GBM varies depending on the location of the tumor and the structures it affects, either directly, through destruction or invasion, or indirectly, due to mass effect and edema. Patients may present with localizing signs, such as focal neurologic deficits, seizures, or strokelike symptoms, or nonlocalizing symptoms, such as severe headaches, if the areas of the brain that are affected are "noneloquent." Temporal lobe tumors may manifest with non-motor seizure activity (eg, olfactory hallucinations) or headache, and frontal lobe tumors may manifest with subtle behavioral changes.
GBM can involve the motor cortex, resulting in generalized tonic-clonic seizures. Occasionally, Jacksonian seizures may occur. These are focal motor seizures that begin with localized tonic-clonic activity of a specific body part such as a finger or a lip, then progress to produce tonic-clonic movements of other muscle groups on the same side of the body. This progression is referred to as the Jacksonian march. There is substantial evidence that if a patient with a GBM presents with seizures, particularly with seizures for more than 18 months, the clinical prognosis is somewhat better than for patients with other presentations (8). The reason for this is not known, but these cases may represent the gradual development of a GBM in a more benign glioma (9).
Uncommonly, GBM is detected as an incidental finding, for example, on computed tomographic (CT) scans of the head obtained because of patient trauma. In this case, the question arises whether the tumor is truly incidental or perhaps precipitated the accidental or traumatic event.
Dissemination of GBM occurs most commonly by local extension, and spread through cerebrospinal fluid is seen in less than 2% of patients (10). Hematogenous metastases are even less common and usually occur in patients who have undergone surgery. The greatest morbidity and mortality from GBM is caused by local growth and direct extension from the site of origin within the brain.
Clinical Presentation