Epidemiology

Patients with intracranial lesions typically have headaches, seizures, focal neurologic changes, weakness, fatigue, or any combination of these findings. Headaches occur in approximately 50% of patients with central nervous system (CNS) tumors; however, brain tumors are uncommon in patients with a headache and normal findings on neurologic examination (<1% of the time).¹ Thus emergency physicians should always consider the presence of a brain tumor in the differential diagnosis but should use neuroimaging judiciously (Table 102.1).^2,3 Focal neurologic changes always warrant further investigation, including laboratory tests, radiographic imaging, and neurologic or neurosurgical consultation (or both).

Table 102.1 Guidelines for Neuroimaging in Patients with a Headache

Adapted from guidelines developed by the U.S. Headache Consortium, American College of Emergency Physicians, and American College of Radiology. American College of Emergency Physicians. Clinical policy: critical issues in the evaluation and management of patients presenting to the emergency department with acute headache. Ann Emerg Med 2002;39:108.

Pathophysiology

Small intracranial lesions can drastically affect important neural pathways within the CNS. Frequently, a non-CNS malignancy is first identified by a neurologic manifestation of a metastatic lesion. Lesions located near or within the ventricular system can be manifested as changes in intracranial pressure (ICP) and thus affect the clinical findings. However, slow-growing lesions of a primary CNS origin located in clinically silent regions of the brain such as the frontal lobe may be present for years before detection.

Autopsy diagnosis reveals that nearly 25% of patients who die of cancer had intracranial metastasis (Fig. 102.1). The lung is the most common origin of brain metastases. Breast cancer (especially ductal carcinoma) has a propensity to metastasize to the cerebellum and the posterior pituitary gland; however, breast cancer that metastasizes to bone tends to not metastasize to the brain.

Fig. 102.1 Axial magnetic resonance image demonstrating a metastatic lesion present at the gray-white matter junction with significant surrounding edema.

The hyperdense focus within the lesion probably represents calcification or blood.

Other common origins of brain metastases are gastrointestinal malignancies (most commonly colon and rectum), renal carcinoma, and melanoma. In contrast, prostate, esophageal, and ovarian cancer and Hodgkin disease rarely metastasize to the brain.

Although metastatic disease is a common form of intracranial mass lesion, other mass lesion considerations include lymphoma (Fig. 102.2), glioblastoma multiforme (Fig. 102.3), astrocytoma, ependymoma, meningioma, oligodendroglioma, medulloblastoma, hemangioblastoma, neurocysticercosis, toxoplasmosis, tuberculoma, tuberous sclerosis, and arteriovenous malformations.

Fig. 102.2 This computed tomography scan demonstrates the classic periventricular homogeneous lesion of a central nervous system lymphoma; it has a ring-enhancing appearance when viewed with contrast enhancement.

Fig. 102.3 The lesion in this computed tomography scan illustrates the characteristic features of glioblastoma multiforme: heterogeneous irregular ring of enhancement, hypointense core, and significant surrounding edema.

Presenting Signs and Symptoms

CNS mass lesions are usually manifested as one of three syndromes: (1) subacute progression of a focal neurologic deficit; (2) seizure; or (3) a nonfocal neurologic disorder such as headache (especially with nocturnal features or occurrence on awakening), dementia, changes in personality, or gait disorder. The presence of systemic symptoms (malaise, fever, weight loss) suggests a metastatic rather than a primary brain tumor or an infectious process such as toxoplasmosis or tuberculoma.⁴

The initial complaint related to a CNS lesion may be attributable to an increase in ICP. Nausea, vomiting, lethargy, and morning headaches are common symptoms that are mistaken for other organ system involvement but are classic findings in patients demonstrating a rise in ICP. Hydrocephalus arising from a strategic location of a CNS lesion can lead to dizziness, ataxia, and vomiting as a result of obstruction to flow of cerebrospinal fluid.

Differential Diagnosis and Medical Decision Making

The initial diagnostic modality in a patient with a new neurologic complaint is a non–contrast-enhanced computed tomography (CT) scan. Most brain tumors causing clinical symptoms are visible on CT scans, and all are visible with the various contrast-enhanced techniques of CT and magnetic resonance imaging (MRI). On nonenhanced CT, brain tumors are visualized by mass effect and altered attenuation. Masses may be hypodense, isodense, or hyperdense with respect to surrounding structures and can be associated with vasogenic edema, which is visualized by low attenuation of the white matter (Box 102.2). Extraaxial lesions can best be appreciated with bone window settings because bone erosion or hyperostosis may be present.

Calcification can be useful in isolating brain tumors. Oligodendrogliomas contain calcification in 90% of cases. Other tumors with calcification include choroid plexus tumors, ependymoma, central neurocytoma, meningioma (Fig. 102.4), craniopharyngioma, teratoma, and chordoma. Nonmalignant lesions such as neurocysticercosis, toxoplasmosis, and tuberous sclerosis exhibit calcific changes on radiographic imaging as well (Table 102.2).

Fig. 102.4 The meningioma seen on this computed tomography scan has the classic extraaxial appearance of this lesion. Meningiomas are often hyperdense and may demonstrate calcification.

Ring enhancement on contrast-enhanced imaging modalities may expand the differential diagnosis to toxoplasmosis, neurocysticercosis, or even multiple sclerosis. Multiple lesions in various stages of development are characteristic of neurocysticercosis. Multiple sclerosis is a common misdiagnosis in the setting of primary CNS lymphoma because both have features of white matter lesions on MRI.

Hemorrhage within a defined lesion on a CT scan should suggest the possibility of an arteriovenous malformation or hemangioblastoma (Fig. 102.5). Contrast-enhanced CT or MRI may identify more than 95% of arteriovenous malformations. Lesions appear as a heterogeneous, hypodense mass with hyperdense regions within the mass; an enhancing rim may also be visible (Fig. 102.6). In patients with negative CT findings but a high index of clinical suspicion, lumbar puncture with cerebrospinal fluid analysis is necessary. If the index of clinical suspicion is high and the diagnosis is suggested by findings on CT, angiography is required to better define the lesion and develop a management strategy. Laboratory analysis of coagulation, including the prothrombin time, partial thromboplastin time, and international normalized ratio, should also be undertaken.

Fig. 102.5 Computed tomography scan with contrast enhancement demonstrating the typical cystic appearance of a cerebellar hemangioblastoma.

A nodular lesion is visible within the wall of the cerebellar cyst.

Fig. 102.6 Arteriovenous malformations, as demonstrated in this non–contrast-enhanced computed tomography scan, are heterogeneous, with hyperdense regions throughout the mass signifying the presence of blood.

Constitutional symptoms should be accounted for when interpreting CNS lesions on radiographic images. Fever or laboratory findings such as leukocytosis or an unusual differential feature (elevated lymphocyte or eosinophil count) may raise suspicion for an infectious cause such as tuberculoma or toxoplasmosis instead of a primary brain tumor or a metastatic lesion.

Treatment

Prehospital evaluation for possible intracranial lesions involves basic emergency medicine principles for airway support and monitoring of breathing. Seizure may be a manifestation that should require standard antiepileptics and airway management. Mass lesions near the pons and medulla, as well as those leading to hemorrhage and a mass effect, will require emergency airway support.

A variety of treatment options are available for the myriad of intracranial lesions possible. Most, if not all modalities should be performed in consultation with neurology and neurosurgery. The majority of lesions require additional specialized diagnostic testing such as serologic analysis and biopsy, which makes the final diagnosis a responsibility of the consultants.

Primary and metastatic brain lesions may require a multifaceted approach to medical care. In the emergency department setting, glucocorticoids and prophylactic antiepileptics (phenytoin, fosphenytoin, phenobarbital) may be given before admission. Surgery, radiation therapy, and chemotherapy are options for further long-term treatment plans, but they are usually tailored to the specific tissue diagnosis when it pertains to a solid mass lesion.⁵

Infectious lesions such as abscesses (Fig. 102.7), neurocysticercosis, toxoplasmosis, and tuberculomas usually require consultation with infectious disease specialists. Serologic examination may prove useful for determining a diagnosis and treatment approach. Antibiotic and antiparasitic medications may be administered under the guidance of these consultants; regimens including clindamycin, albendazole, praziquantel, sulfadiazine, and pyrimethamine may be instituted with or without glucocorticoids.

Fig. 102.7 This irregularly shaped mass may ultimately reveal edema surrounding a large intrinsic brain tumor on subsequent imaging, but this lesion is a result of a central nervous system abscess.

Special situations include hemorrhaging lesions, such as metastatic lesions or arteriovenous malformations, which may necessitate the use of coagulation factors such as fresh frozen plasma, platelets, or factor VII given the location, mass effect, and patient-specific comorbid conditions.

Follow-Up, Next Steps in Care, and Patient Education

Most lesions that are discovered on CT or are due to a neurologic abnormality require further inpatient diagnosis and treatment as stated in the previous section. Patients with meningiomas or those with a known diagnosis of a chronic condition such as tuberous sclerosis may be discharged and close follow-up with primary and specialty physicians arranged. Any new lesion (except for a solitary meningioma, for example) or signs of a mass effect require emergency consultation with a specialty service.