Images courtesy of Lennard A. Nadalo, MD
Images courtesy of Lennard A. Nadalo, MD
Author
Lennard A. Nadalo, MD
Clinical Professor, Department of Radiology
University of Texas Southwestern Medical School
Consulting Staff
Envision Imaging of Allen and Radiological Consultants Association
Dallas, Texas
Disclosure: Lennard A. Nadalo, MD, has disclosed no relevant financial relationships.
Editor
Lars Grimm, MD
House Staff
Department of Internal Medicine
Duke University Medical Center
Durham, North Carolina
Disclosure: Lars Grimm, MD, has disclosed no relevant financial relationships.
Reviewer
Jose Varghese, MD
Associate Professor of Radiology
Boston University School of Medicine
Boston, Massachusetts
Disclosure: Jose Varghese, MD, has disclosed no relevant financial relationships.
The MRI is performed. The axial fluid-attenuated inversion-recovery (FLAIR) image (left) demonstrates periventricular edema (yellow arrow) and a focal round white matter low-intensity lesion (white arrow). The coronal post-gadolinium-enhanced T1-weighted image (right) reveals extensive basilar meningeal enhancement (yellow arrows) and ring enhancement surrounding the lesion in the right hemisphere (white arrow). The basilar location of the meningeal enhancement in combination with the parenchymal lesions is most consistent with cerebral tuberculosis, which was eventually cultured from the cerebrospinal fluid.
Central nervous system (CNS) tuberculosis can be divided into 4 stages:
• Cerebritis stage - nonspecific edema, ill-defined enhancement;
• Solid, granulomatous stage - enhancing nodules with surrounding edema;
• Central caseation stage - central hypointensity on T2 peripheral enhancement; and
• Involutional stage - multiple calcified lesions.
Imaging of the chest reveals additional characteristic features of tuberculosis. The frontal chest x-ray (left) reveals enlargement of the right hila and mediastinum (double-headed arrow) consistent with adenopathy. There is also an infiltrate in the right lower lobe (angled arrow). Corresponding contrast-enhanced CT confirms adenopathy in the right hilum (white arrow).
A young patient with known HIV disease presented with sudden onset of headache and reduced level of consciousness. An MRI is ordered, and a representative axial image from a postcontrast T1-weighted image of the brain is shown revealing multiple enhancing lesions (white arrows).
What is the primary diagnostic consideration? What are other differential considerations?
The primary diagnostic consideration in a patient with HIV with multiple enhancing lesions is toxoplasmosis. Other differential considerations would include tuberculosis and metastatic lesions. Toxoplasmosis is less likely to have as vivid meningeal thickening with enhancement as CNS tuberculosis. Spectroscopy in lymphoma often demonstrates elevated choline with some elevation of lactate and lipid in enhancing areas of the lesion. In contrast, toxoplasmosis is associated with marked elevation of lactate and lipid with depression of normal brain metabolites (choline, creatine, and N-acetyl aspartate).
A young patient presents to the emergency department with fever and headache. He reports that he was recently diagnosed with pneumonia. The noncontrast CT scan reveals a poorly defined area of hypoattenuation in the posterior parietal brain consistent with edema.
What is the most likely cause for the edema, and what is the patient at risk of developing?
The posterior parietal edema is most likely due to cerebritis. A short-term follow-up CT scan with contrast enhancement reveals an abscess. Note the hypoattenuating necrotic core (black arrow) with a rim of enhancement (yellow arrow) and surrounding edema (white arrow). This is consistent with an early capsule phase of a cerebral abscess. Most abscesses are produced by pyogenic bacteria, particularly streptococci and staphylococci.
Infectious agents are able to access the CNS via 1 of 4 mechanisms:
• Direct spread from otitis media, mastoiditis, sinusitis, or dental infection;
• Hematogenous seeding;
• Spread from retrograde thrombophlebitis preceded by empyema, meningitis, or both; or
• Congenital infection.
This postgadolinium T1-weighted MRI is from a patient with persistent fevers and headache who did not respond to intravenous antibiotics. In the right frontal lobe is a thick-walled abscess with features similar to CT: low central signal (double white arrows) and peripheral increased signal (black arrow). This abscess is in the "thick-walled" stage and is not responsive to antibiotics.
What are other differential considerations for a ring-enhancing lesion?
The differential considerations for a ring-enhancing lesion are metastatic disease, infarction, and lymphoma. Metastatic lesions are more likely to be multiple. Infarction is more likely to occur at the gray-white matter junction and have mass effect. Lymphoma is the great mimicker and can present as anything.
This T1-weighted post-gadolinium-enhanced MRI reveals a primary abscess (white asterisk) with a smaller daughter abscess (black asterisk). Ring enhancement (black arrows) and surrounding edema (white arrows) are present.
This patient presented with worsening neurologic defects following surgical repair of an open skull fracture and subdural hematoma. There has been external-to-internal infectious spread. The CT scan reveals an abscess of the subgaleal space (SGA) with extension to the epidural space (EDA) and left cerebral hemisphere (CA). There is also edema (yellow arrow) and ring enhancement (white arrow).
Superficial skin and sinus infections can lead to abscess development within the orbit or brain. An MRI is performed in a patient with left orbital swelling and proptosis. The axial fast spin-echo inversion-recovery image shows orbital cellulitis (yellow arrows) with the development of a subsequent intraconal abscess (white arrows) and venous thrombosis.
This middle-aged, diabetic man presented with headache, fever, and diplopia. His MRI reveals a large right frontal lobe abscess (black arrow) associated with midline shift (double-headed arrow). The infection migrated from the right ethmoid air cells, through the medial right orbit, and up into the brain (curved dotted red arrow). The diagnosis of cerebro-rhino-orbital phycomycosis was made after Aspergillus was cultured. Immunosuppressed persons, particularly patients with poorly controlled diabetes (often in the setting of metabolic acidosis), are susceptible to this condition. In contrast to immunocompetent individuals whose immune system phagocytizes the spores, immunocompromised patients experience spore proliferation and potentially rapid spread of infection.
The axial CT scan reveals hydrocephalus with a ventriculoperitoneal shunt (white arrow) and an intraventricular mass (yellow arrow). The patient was found to have neurocysticercosis with an intraventricular cystic mass. Ventriculoperitoneal shunt failure occurs from the high protein count that clogs the shunt tubing. Note the sulcal flattening along the periphery secondary to the hydrocephalus.
A 24-year-old male presents with severe headache, cough, and fever. Since recovering from a pulmonary infection, he has developed confusion and numbness in his extremities. His lumbar puncture reveals mildly increased protein, increased monocytes, and no evidence of bacterial or fungal organisms. An axial FLAIR MR image demonstrates multiple areas of increased signal intensity (yellow arrows).
What is the most likely diagnosis?
The patient has developed viral encephalitis. Coronal T2-weighted MRI demonstrates increased T2 signal (yellow arrows) consistent with edema. If long-standing, these changes may be due to demyelination, but in the acute setting edema is more likely. Viral encephalitis, typically following a recent viral infection, can lead to vertigo, confusion, and nonspecific neurologic complaints. In this patient antibodies indicated viral encephalitis.
The MRI did not reveal a stroke, but rather an area of increased signal within the cerebellum. The axial FLAIR image (left) demonstrates increased signal (black arrow) with mass effect and compression of the fourth ventricle. The coronal T1-weighted postcontrast image (right) demonstrates a central zone of enhancement (black arrow) with surrounding decreased signal (white arrow) from edema. Cultures from the abscess cavity grew Nocardia.
Images courtesy of Lennard A. Nadalo, MD
Author
Lennard A. Nadalo, MD
Clinical Professor, Department of Radiology
University of Texas Southwestern Medical School
Consulting Staff
Envision Imaging of Allen and Radiological Consultants Association
Dallas, Texas
Disclosure: Lennard A. Nadalo, MD, has disclosed no relevant financial relationships.
Editor
Lars Grimm, MD
House Staff
Department of Internal Medicine
Duke University Medical Center
Durham, North Carolina
Disclosure: Lars Grimm, MD, has disclosed no relevant financial relationships.
Reviewer
Jose Varghese, MD
Associate Professor of Radiology
Boston University School of Medicine
Boston, Massachusetts
Disclosure: Jose Varghese, MD, has disclosed no relevant financial relationships.
Case Quiz: A Can't-Miss Abdominal Catastrophe
Case Quiz: An Unusual Diagnosis in a Young Woman With Abdominal Pain
Common but Dangerous Plant Poisonings
Infectious Skin Conditions Not to Miss
The Shattered Pelvis
