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Neuroradiology Case of
the Week
Case 158
Labib Syed, MD, MPH and PL Westesson MD, DDS, PhD
Clinical
Presentation: The patient is a 42-year old male who presented to the Emergency Department with a week long history of a left frontal headache, shortness of breath and sinus discharge. A chest x-ray reveals a mass in the LUL for which a CT scan of the chest, abdomen and pelvis are ordered. Subsequently, a brain MRI is requested.
Radiological Findings:
MRI: Heterogeneously enhancing mass which demonstrates low signal on T1 and T2-weighted images located in the left frontal lobe with extension into the ethmoid sinuses. There is a significant amount of surrounding edema which demonstrates increased signal on FLAIR and T2-weighted images. This results in mass effect with regional sulcal and ventricular effacement. There is also subfalcine herniation.
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| Figure 1: Axial FLAIR image. |
Figure 2: Axial T2WI image. |
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Figure 3: T1WI image with contrast. |
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| Figure 4: Coronal SPGR image with contrast. |
Figure 5: Coronal SPGR image with contrast. |
CT: Multifocal spiculated mass in the left upper lobe with cavitation and necrosis.
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Figure 6: Lung CT. |
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Figure 7: Lung CT. |
Differential Diagnosis:
- Metastasis
- Primary brain tumor (glioma)
- Olfactory neuroblastoma (ethesioneuroblastoma)
Diagnosis: Metastatic poorly differentiated squamous cell carcinoma consistent with lung primary
Discussion: In the adult population, metastasis represents the most common etiology of both supratentorial and infratentorial masses. The primary tumors that spread to the brain are lung, breast, melanoma, renal and gastrointestinal tumors. Among these, presentation with a solitary metastatic lesion is noted in 30% - 50% of cases with lung and breast primaries accounting for the largest share. If presented with a solitary brain lesion, a complete clinical and radiographic search must be undertaken to determine a primary. If none is found, the differential becomes a glioma. This patient presents with a solitary intraxial mass with a known squamous cell lung primary. Consequently, metastatic disease climbs to the top of the differential.
In general, metastatic disease presents as enhancing, well-defined lesions with a moderate amount of surrounding edema. Classically, these lesions are deposited at the junction of the gray-white matter because of the small caliber of vessels in this region with possible extension into the cortex or white matter. As these lesions follow normal flow dynamics, the carotid system is involved to a much greater extent than the vertebrobasilar system with a predilection for the middle cerebral artery distribution.
Typical imaging characteristics of metastatic disease on unenhanced CT include decreased attenuation lesions unless hemorrhagic and hypercellular components are present. On MRI, these lesions demonstrate decreased signal on unenhanced T1WI with variable signal intensity on T2WI depending on the presence of hemorrhage, intratumoral necrosis, cyst formation, high nuclear/cytoplasmic ratios or paramagnetic content. Variable enhancement is a feature of nearly all metastatic disease. However, the patterns of enhancement may vary widely including: solid, ring like, regular, irregular, homogeneous or heterogeneous. In contrast to gliomas, metastatic disease tends to have better definition of its borders. Additionally, the degree of vasogenic edema is often out of proportion to the size of the lesions unless they are cortical metastasis where edema may be minimal or absent. In these cases, T2WI may miss the metastatic lesion and contrast administration becomes essential.
Another differential consideration is the olfactory neuroblastoma or esthesioneuroblastoma. This tumor arises from the olfactory nerves in the nasal vault. There is a bimodal peak involving pediatric and middle aged adults with a predilection for males. Clinically, these patients present with epitaxis, nasal obstruction and decrease in olfactory function. ; These are fairly aggressive lesions and readily cross the cribiform plate to enter the intracranial space. On imaging, esthesioneuroblastomas tend to have decreased signal on T2WI with avid enhancement.
References:
- Grossman RI, Yousem DM. Neuroradiology: The Requisites, 2nd ed. St.
Louis: Mosby; 2003.
- Schellinger PD, Meinck HM, Thron A. Diagnostic accuracy of MRI
compared to CCT in patients with brain metastases. J Neurooncol 1999;
44(3): 275-81. [Medline]
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