Alok A. Bhatt

The “pool sign” of metastatic adenocarcinoma

The differential of a newly discovered solitary intracranial mass is a primary intracranial neoplasm and metastatic disease. Differentiating between the two entities on imaging is difficult, though there are clues on conventional imaging that suggest one over the other. The purpose of this article is to describe a new imaging finding on T2-weighted imaging, the “pool sign,” that may be specific for metastatic adenocarcinomas and can help differentiate a solitary metastasis from a primary CNS neoplasm. We present a series of four patients with initial magnetic resonance imaging of a solitary intracranial mass demonstrating the “pool sign,” and therefore predicted to be metastatic adenocarcinoma. All of these cases were confirmed to be metastatic adenocarcinoma on pathology.

Location, length, and enhancement: systematic approach to differentiating intramedullary spinal cord lesions

PurposeIntramedullary spinal cord abnormalities are often challenging to diagnose. Spinal cord biopsy is a high-risk procedure with the potential to cause permanent neurological injury. Magnetic resonance imaging is the modality of choice for diagnosis and preoperative assessment of patients with spinal cord abnormalities. The radiologist’s ability to narrow the differential diagnosis of spinal cord abnormalities has the potential to save patients from invasive approaches for diagnosis and also guide appropriate management.Approach/methodsThis article will provide a systematic approach to the evaluation of intramedullary spinal cord lesions—with emphasis on location, length and segment distribution, and enhancement pattern—to help narrow the differential diagnosis. In doing so, we will review various spinal cord pathologies, including demyelinating and metabolic conditions, neoplasms, and vascular lesions.Summary/conclusionAlthough intramedullary spinal cord abnormalities can be a challenge for the radiologist, a systematic approach to the differential diagnosis with a focus on lesion location, cord length and segment involvement, as well as enhancement pattern, can greatly help narrow the differential diagnosis, if not synch the diagnosis. This strategy will potentially obviate the need for an invasive approach to diagnosis and help guide treatment.Teaching points• Imaging diagnosis of intramedullary spinal cord lesions could obviate cord biopsy.• Evaluation of cord lesions should focus on location, length, and enhancement pattern.• In demyelination, the degree of cross-sectional involvement is a distinguishing feature.

Imaging of the sublingual and submandibular spaces

Divided by the mylohyoid muscle, the sublingual and submandibular spaces represent a relatively small part of the oral cavity, but account for a disproportionate amount of pathological processes. These entities are traditionally separated into congenital, infectious/inflammatory, vascular and neoplastic aetiologies. This article reviews the relevant anatomy, clinical highlights and distinguishing imaging features necessary for accurate characterisation.Teaching Points• The mylohyoid sling is a key anatomical landmark useful in surgical planning.• Congenital lesions and infectious/inflammatory processes constitute the majority of pathology.• Depth of invasion is key when staging tumours in the oral cavity.

Non-traumatic causes of fluid in the retropharyngeal space

There are multiple reasons for imaging the soft tissues of the neck in the emergency setting, in particular when symptoms are vague or if there is worry for complications from a certain clinical diagnosis. When fluid is seen in the retropharyngeal space, it is important to pay attention to history and look at key structures in the neck. This article will discuss anatomy of the retropharyngeal space, followed by four causes of fluid within the space that the radiologist is likely to encounter in the emergency setting: tonsillitis/pharyngitis, acute calcific tendinitis of the longus colli muscles, internal jugular vein thrombosis, and post-radiation changes. It is important to recognize these entities because each has different clinical implications and management.

Hemorrhagic and non-hemorrhagic causes of signal loss on susceptibility-weighted imaging

Susceptibility-weighted imaging (SWI) plays a key role in an emergency setting. SWI takes the intrinsic properties of materials being scanned and creates a visual representation of their effects on the magnetic field, thereby differentiating a number of pathologies. Magnetic resonance imaging (MRI) is now more often used, especially when computed tomography (CT) is inconclusive or even negative. Often, clinicians prefer to obtain an MRI first. This article will review the various hemorrhagic and non-hemorrhagic causes of low signal on SWI. There will be a focus on the distribution patterns of low signal on SWI in pathologies such as diffuse axonal injury, cerebral amyloid angiopathy, and cerebral fat embolism. It is important to recognize these patterns of susceptibility, as the radiologist may be the first to give an accurate diagnosis and therefore, directly impact clinical management.

Beyond stroke—uncommon causes of diffusion restriction in the basal ganglia

In the emergency setting, a regional area of restricted diffusion involving the basal ganglia typically represents an acute infarct due to small vessel occlusion. However, it is important to consider additional differentials, specifically systemic causes. This article will review anatomy of the basal ganglia and pertinent associated vasculature, followed by other entities that can be a cause of restricted diffusion. These include hemolytic uremic syndrome, hypereosinophilic syndrome, fat embolism, meningitis, and hypoxic-ischemic injury. It is important to recognize presenting findings in these conditions, as the radiologist may be the first to give an accurate diagnosis or prompt additional testing.

Post-operative complications of craniotomy and craniectomy

Craniotomy and craniectomy are widely performed emergent neurosurgical procedures and are the prescribed treatment for a variety of conditions from trauma to cancer. It is vital for the emergency radiologist to be aware of expected neuroimaging findings in post-craniotomy and craniectomy patients in order to avoid false positives. It is just as necessary to be familiar with postsurgical complications in these patients to avoid delay in lifesaving treatment. This article will review the commonly encountered normal and abnormal findings in post-craniotomy and craniectomy patients. The expected postoperative CT and MRI appearance of these procedures are discussed, followed by complications. These include hemorrhage, tension pneumocephalus, wound/soft tissue infection, bone flap infection and extradural abscesses. Complications specifically related to craniectomies include extracranial herniation, external brain tamponade, paradoxical herniation, and trephine syndrome.

Acute paraplegia in a patient with repaired coarctation of aorta

A 77-year-old neurologically intact woman presented in hypertensive crisis (blood pressure [BP] 220/110 mm Hg) resulting in pulmonary edema. The patient had a history of remote (over 40 years) repaired aortic coarctation, breast cancer in remission, hypertension managed with 6 antihypertensive medications, and allergy to iodinated contrast. Her BP was reduced to as low as 134/26 mm Hg. Subsequently she developed acute paraplegia. Examination revealed nonlocalizing lower back and abdominal pain. Tibial pulses were absent, but extremities remained warm to touch. On neurologic examination, the abnormal findings were present only in the lower extremities, which were both flaccid with 0/5 strength and 0/4 deep tendon reflexes. Plantar responses were mute. Sensory perception to all primary sensory modalities was absent with a sensory level to pinprick at L1 dermatome. She was unable to generate rectal sphincter tone. Bladder dysfunction could not be assessed due to Foley catheter in place.

Acute ocular traumatic imaging: what the radiologist should know

Acute ocular trauma accounts for a substantial number of emergency department visits in the USA, and represents a significant source of disability to patients; however, the orbits remain a potential blind spot for radiologists. The goal of this article is to review the relevant anatomy of the orbit and imaging findings associated with commonly encountered acute ocular traumatic pathology, while highlighting the salient information which should be reported to the ordering clinician. Topics discussed include trauma to the anterior and posterior chamber, lens dislocations, intraocular foreign bodies, and open and contained globe injuries.