Non-ketotic, hyperglycemic, hemichorea

Findings

Figure 1: CT scan reveals unilateral hyperdensity of the left lentiform nucleus and the head of the left caudate nucleus with sparing of the intervening internal capsule that corresponds to abnormal gemistocytic astrocyte production. No significant abnormal enhancement is identified.
Figure 2: MR images demonstrate hyperintense T1 and hypointense T2 and diffusion weighted image signals in the same distribution as the CT abnormality. There is no significant abnormal enhancement and no mass effect.
Figure 3: Follow-up imaging performed 14 weeks after initial presentation demonstrates preserved high signal in the left basal ganglia without mass effect or enhancement. T2-weighted signal has changed from low to high intensity, perhaps representing interval gliosis.


Diagnosis: Non-ketotic, hyperglycemic, hemichorea


The differential diagnosis for the new-onset hemichorea includes: stroke, hemorrhage, tumor, infectious disease, neurodegenerative disorders and non-ketotic, hyperglycemic hemichorea.
Particular to the diagnosis of NHH, the characteristically unilateral transient extrapyramidal motions resolve following glycemic control.
Cerebral images of these patients consistently have shown unilateral CT hyperattenuation and unilateral MRI T1-weighted hyperintensity in the striatum contralateral to the side of the transient, extrapyramidal motion disorder.
Typically, an elderly diabetic patient presents with new-onset hemichorea as well as glucose levels ranging from 400 to 600 mg/dl with an HBA1c greater than 13%.

Non-ketotic, hyperglycemic hemichorea (NHH) was first described by Rector, et al. in 1982. Thirty-three cases of NHH have been identified in our recent review of literature. The most commonly reported location of a lesion has been in the putamen. Kumral, et al. have suggested that the anterior putamen needs to be involved for transient extrapyramidal motions to occur. The distinct imaging findings are hyperattenuation on CT and hyperintensity on T1-weighted MRI. This Case in Point’s images concur with these distinct image findings.

The onset of NHH has been attributed to petechial hemorrhage with blood-brain barrier breakdown, cerebral ischemia leading to dysfunction of the GABAnergic projection neurons and gliosis. Blood glucose levels of 159 to 647 mg/dl have initiated non-ketotic hyperglycemia resulting in hemichorea. More commonly reported values exceed 500 mg/dl.

There is accumulating consensus on the pathophysiology of NHH. Human autopsy, animal studies, human biopsy and MR spectroscopy evidence that NHH results in mild infarction with gliosis and concurrent accumulation of pathologically swollen, nucleus-eccentric astrocytes, known as gemistocytes. MRI findings have been attributed to gemistocyte deposition along axons. Rat model and human autopsy histopathology have revealed T1-weighted, hyperintense, gliotic brain tissue with abundant gemistocytes.

This Case in Point documents new hyperintensity in the areas of previous hypointensity on follow-up T2-weighted MRI and FLAIR images. It is plausible such images represent areas of delayed gliosis or scar tissue formation.

Fourth ventricular ependymoma with foramen of Luschka & Magendie extension

Findings

CT paranasal sinuses: Normal sinuses. Incidental note of ventricular dilatation. Partial visualization of 4th ventricular mass.
MRI Brain: Abnormal heterogeneously enhancing mass within the posterior fossa, potentially arising from the floor of the fourth ventricle and causing moderate obstructive hydrocephalus. Lobular extension of tumor via the bilateral (left > right) foramen of Luschka and foramen of Magendie.

Differential diagnosis:
- Ependymoma
- Medulloblastoma
- Atypical teratoid/rhabdoid tumor
- Cerebellar pilocytic astrocytoma


Diagnosis: Fourth ventricular ependymoma with foramen of Luschka & Magendie extension masquerading as sinusitis


Discussion

Arising from the ependymal lining of the ventricles, ependymomas constitute one-tenth of primary CNS tumors in children. 90 percent of the tumors are intracranial which helps ependymomas rank number three among pediatric brain tumors. The majority of the intracranial epenymomas are infratentorial (about two-thirds). The remaining one-third of the intracranial variety are found around the periventricular white matter.

An equal distribution has been reported in males and females. No known race predilection noted. The mean age of diagnosis is 5 to 6 years of age. The clinical presentation is often non-specific. However, it is usually related to increased intracranial pressure. The classic triad (if present) includes morning headache, relieved by vomiting and improvement with progression of the day. Other signs/symptoms can include irritability, gait problems, fatigue, personality change and declining performance at school.

Gross total surgical resection and radiation therapy are the mainstays of treatment. The fiver year rate of survival is estimated close to 55 percent. Poorer outcomes have been reported in children with incomplete resection. The exact role of chemotherapy is still under investigation.


Radiologic overview of the diagnosis

CT and MRI are the primary modalities for imaging brain tumors in children. A CT may be obtained initially. However, MRI with contrast is more useful for component characterization and tumor extension.

Regardless of imaging modality, the best diagnostic clues include inhomogeneous appearance and pliability. The tumor is known for its ability to squeeze through the fourth ventricle into the cisterns. Another important diagnostic feature is ill defined interface with the floor of the fourth ventricle.

On CT, calcifications are present in half of these tumors. Cystic and hemorrhagic components can also be seen. With fourth ventricular tumors, hydrocephalus can be present. The enhancement pattern is typically heterogeneous.

On MRI, an inhomogeneous appearance persists with T1 isointensity to hypointensity. The tumor is isointense to hyperintense of T2 weighted images. Areas with calcification or blood products are T1 hyperintense and T2 hypointense. On gradient images, the calcification demonstrates blooming artifact. The post contrast enhancement pattern remains inhomogeneous with overall mild to moderate enhancement. High quality sagital sequences should be included in the MRI protocol. A sagital image can help identify the point of origin (floor of fourth ventricle = ependymoma, roof of fourth ventricle = medulloblastoma). MR spectroscopy cannot reliably differentiate between this and other tumors. However, lactate and choline peak elevation is present with decrease in NAA.

Hydatid disease involving the brain (Echinococcus granulosus infection)

Findings

T1 (Figure 1) and T2 (Figure 2) weighted MR images demonstrate two homogeneous cysts with signal intensity similar to cerebrospinal fluid and very thin-walls (yellow arrows). There is significant mass effect on the lateral ventricular system.
Contrast enhanced MRI (Figure 3) shows lack of enhancement of the cyst walls.


Diagnosis: Hydatid disease involving the brain (Echinococcus granulosus infection)


Intracranial granulosus echinococcosis occurs in only approximately 2% of cases of hydatid disease.
E. granulosus infection of the brain presents with one or more homogeneous, thin-walled cysts.
Cyst signal is isointense relative to cerebrospinal fluid.
The cyst wall typically lacks gadolinium enhancement.
Usually there is no perilesional edema.

Hydatid disease is a worldwide zoonosis produced by the larval stage of the Echinococcus tapeworm. The two main types of hydatid disease are caused by E granulosus and E multilocularis. E granulosus is the more common type, whereas E multilocularis is less common but more invasive, mimicking a malignancy. It is commonly seen in the great grazing regions of the World, particularly the Mediterranean region, Africa, South America, the Middle East, Australia, and New Zealand.

Dogs or other carnivores are definitive hosts, whereas sheep or other ruminants are intermediate hosts. Humans are secondarily infected by the ingestion of food or water that has been contaminated by dog feces containing the eggs of the parasite.

Intracranial granulosus echinococcosis occurs in only approximately 2% of cases of hydatid disease, typically involving the cerebral parenchyma, especially the parietal lobes, corresponding to the middle cerebral artery watershed territory. Intracranial subarachnoid spaces are the second most common location of the disease in the CNS, although their occurrence is far less frequent. Cases of cerebral aqueduct cyst, gigantic cyst arising from the diploe of cranial bones with intracranial extension, and intradural spinal hydatid cysts have been reported. Cysts are usually single and may be unilocular or multilocular. Cerebral hydatid cyst is more common in children than in adults.

At MRI, cerebral hydatid disease generally appears unilocular and is isointense relative to cerebrospinal fluid. The lack of surrounding edema and the marked mass effect make it easy to distinguish cerebral hydatid disease from abscess and cystic tumor. The presence of a hypointense rim, especially on T2-weighted MR images, is characteristic of hydatid cyst of the brain. Cerebral hydatid cyst is generally solitary but may be multiple when it ruptures spontaneously or due to trauma or surgery. Multivesicular cysts are rare in the brain. Calcification occurs in less than 1% of cases.

Brain death from meningitis secondary to ear infection

Findings

Initital head / temporal CT: Pneumocephalus along the left falx of unknown etiology. No evidence of intracranial lesion, midline shift, or intracranial hemorrhage. No fracture of the temporal bones. Widening of the left lambdoid suture with well corticated borders, inconsistent with fracture. Fluid is present in the mastoid air cells bilaterally.

Follow-up CT: Unchanged pneumocephalus. Loss of the suprasellar and quadrigeminal plate cisterns consistent with herniation. Decreasing differentiation between the gray and white matter consistent with edema. Fluid again was seen in the mastoid air cells bilaterally.

Nuclear medicine study: No evidence of flow/perfusion to brain either on the early dynamic images or on the delayed images.

Differential diagnosis:
- Skull fracture
- Meningitis

Epilogue: Patient's girlfriend reported he was diagnosed with an ear infection, but did not fill the prescription. After toxicology consult, possiblity of meningitis was raised. While still in ER the second head CT was done which showed changes of diffuse brain hypoxia with cerebral edema and herniation. Examination at this point revealed fixed and dilated pupils with no brainstem reflexes. ICP monitor was placed showing pressure was significantly elevated, unable to be controlled with hyperosmolar therapy. A nuclear medicine scan was obtained and showed no evidence of flow or perfusion to the brain, findings consistent with brain death when taken in correlation with clinical findings.


Diagnosis: Brain death from meningitis secondary to ear infection


Key points

Differential diagnosis of Pneumocephalus
- Traumatic 74%
May be found within any compartment from skull, skull base, paranasal sinus, or mastoid fracture
3% of all skull fractures
8% of all paranasal sinus fractures
- Neoplasm involving sinus 13%
Osteoma, pituitary adenoma, mucocele, epidermoid, paranasal sinus malignancy
- Iatrogenic 4%
Lumbar puncture, craniotomy, craniectomy, ventriculostomy, ICP monitor placement
- Infectious 9%
Rare sequela of gas-producing infection
Typically sinusitis or mastoiditis
- Regardless, pneumocephalus itself is not a problem—what's causing it?

Epidural
- Remains localized
- Air will not necessarily move with changes in head position

Subdural
- Air-fluid levels
- Moves with changes in head position
- Confluent
- Tension pneumocephalus may result in "Mount Fuji sign"—subdural air separates/compresses frontal lobes, creating widened interhemispheric space between frontal lobe tips—mimics silhouette of Mt Fuji.

Subarachnoid
- Multifocal
- Non-confluent

CT: Imaging tool of choice
MRI: Foci of absent signal on all sequences

Inverting papilloma

Findings

Multiple axial T1 images without and with intravenous gadolinium through the nasal cavity reveal a lobulated mass occupying the nasal passages (Figure 1, Figure 2 and Figure 3) with extension into the anterior cranial fossa (Figure 4 and Figure 5) as well as the right maxillary sinus (Figure 3).
This lesion demonstrates heterogeneous enhancement (Figure 2, Figure 3 and Figure 4) on post contrast axial and coronal T1 sequences. There is also thinning and remodeling of the bony septa of the nasal cavity on both axial CT (Figure 6 and Figure 7) and coronal CT reconstructions (Figure 8).

Differential diagnosis
- Esthesioneuroblastoma
- Antral choanal polyp
- Mucocele
- Allergic fungal sinusitis
- Squamous cell carcinoma
- Adenocarcinoma
- Juvenile nasoangiofibroma


Diagnosis: Inverting papilloma


Benign but bulky tumor that usually originates from the lateral nasal wall in the nasal cavity as well as the ethmoidal and maxillary sinuses
"Inverting" term comes from endophytic growth of epithelia into the surrounding stroma
Can often harbor a concurrent squamous cell carcinoma, which enhances more homogeneously and centrally

Inverting papilloma is a benign, slow-growing tumor of epithelial origin that occurs most commonly within the nasal cavity and paranasal sinuses. The term ‘inverting’ stems from the observation on pathology that proliferation of epithelial cells occurs into the surrounding stroma by endophytic growth rather than exophytic growth, as is expected.

Clinically, the typical patient is a male between the ages of 40-60 years. The most frequent complaints are unilateral nasal obstruction, stuffiness, epistaxis, dysosmia, rhinorrhea and pain. Inverting papilloma can affect the orbits by proptosis or by deformation of the bony orbits.

Radiologically, inverting papilloma is a homogeneous and lobulated lesion with scattered calcification in a variety of patterns. On CT, it can often have a lobulated (‘cerebriform’) appearance which has been reported to be very specific. It enhances heterogeneously and peripherally in contrast to squamous cell carcinoma, which enhances more homogeneously and centrally. Inverting papilloma most often arises from the lateral nasal wall, adjacent to the middle turbinate and posterior to the uncinate process. If it affects the paranasal sinuses, it most commonly involves the ethmoidal and maxillary sinuses. Enlargement of inverting papilloma can produce local bone thinning, bowing or erosion. It often grows through the nasal choana into the nasopharynx.

Concurrent squamous cell carcinoma has been reported in about a quarter of cases. This is seen as bony destruction, multicentric soft tissue extension and nodal metastases. CT and MR are complementary in assessing the extent of this tumor’s involvement as this is crucial to planning accurate and complete surgical resection. Treatment involves endoscopic surgical resection but recurrence is rather common.

Rheumatoid arthritis with vertical subluxation and an associated anterior atlantoaxial subluxation at C1-C2

Findings

Figure 1: Axial CT image of the brain displayed in bone windows at the level of the posterior fossa. The dens is subluxed superiorly into the foramen magnum.
Figure 2: Lateral radiograph of the cervical spine in the neutral position. The superior half of the odontoid process is difficult to visualize secondary to overlapping osseous structures. The position of the anterior arch of the atlas in relation to the dens is also not clearly demonstrated. Chronic degenerative changes are incidentally noted at C3-C4.
Figure 3 and Figure 4: T1-weighted and T2-weighted sagittal MR images of the cervical spine. The dens is seen to extend superiorly, occupying a position within the foramen magnum. The anterior arch of the atlas has an abnormal position in relation to the odontoid process, maintaining a position equivalent to the plain film finding of Clark station II. The posterior aspect of the anterior atlas also has a position more than 2.5 mm from the anterior border of the dens.


Diagnosis: Rheumatoid arthritis with vertical subluxation and an associated anterior atlantoaxial subluxation at C1-C2


Vertical subluxation is a malalignment disorder of the cervical spine affecting the C1-C2 junction in patients with rheumatoid arthritis. The definition of vertical subluxation is synonymous with other frequently used terms such as atlantoaxial impaction, vertical atlantoaxial subluxation, odontoid upward migration, cranial settling, and basilar invagination of the odontoid process. Vertical subluxation has been reported in 5 to 22% of patients with rheumatoid arthritis. The inflammatory arthropathy of rheumatoid arthritis alters the synovial structures of the cervical spine and predisposes patients to anterior, vertical, lateral and/or posterior atlantoaxial subluxation. Although anterior subluxation is the most frequent to occur, vertical subluxation is considered to have the highest potential for associated neurological complications.

Rheumatoid arthritis causes progressive erosive changes of the osseous and articular structures at C1-C2, which may subsequently lead to collapse of the facet joints. This process of vertical subluxation stems from extension of the superior aspect of the odontoid process into the foramen magnum. Potentially devastating neurological complications or sudden death can occur as the result of compression of the adjacent brainstem, spinal cord, cranial nerve roots, spinal and/or vertebral arteries. Vertical subluxation may also appear in association with anterior subluxation, which results from the disruption of the transverse atlantoaxial ligament by pannus formation.

Initial evaluation can be performed with plain radiographs. Not all patients with inflammatory arthropathy of the cervical spine are symptomatic, demonstrating the need for a high index of clinical suspicion in patients with chronic rheumatoid arthritis. A lateral radiograph of the cervical spine in a neutral position can be evaluated for vertical subluxation. A multitude of techniques, with varying degrees of sensitivity and specificity, exist for the radiographic analysis of vertical subluxation on plain film. A common methodology includes the use of a MacGregor’s line, which extends from the posterior hard palate to the occiput. An 8 mm extension of the dens above the MacGregor’s line in men and 9.7 mm in women has been described as proof of vertical subluxation. Clark station is another simple method, with the odontoid process divided into three equal parts in length within the sagittal plane. The most superior section is station I, the middle section is station II, and the most inferior section is station III. If the anterior arch of the atlas lies anterior to station II or III of the dens, then vertical subluxation is present. A potential pitfall of radiographic analysis is nonvisualization of the dens, which may occur as a result of overlapping osseous structures, osteopenia or extensive erosion of the dens by rheumatoid arthritis. In addition to the evaluation for vertical subluxation on the lateral film, the distance between the anterior arch of the atlas and the dens must be measured. A distance of greater than 2.5 mm in adults indicates an associated anterior subluxation.

Cross-sectional imaging can be utilized in difficult cases or symptomatic patients with equivocal plain films to establish a diagnosis. The multiplanar capabilities of computed tomography (CT) and magnetic resonance (MR) imaging can better define the anatomic relationships among the occiput, axis and atlas than plain film radiographs. Any destructive osseous changes related to rheumatoid arthritis are also best demonstrated by CT. When neurological compromise is suspected, the modality of choice for brain or spinal cord injury is MR.

Parotid gland sialolithiasis

Findings

Parotid duct stone, dilated duct, and associated L parotid enlargement with some mild inflammatory changes.


Diagnosis: Parotid gland sialolithiasis


Key points

Sialolithiasis

80-92% sublingual; 6-20 % parotid; 1-2% minor salivary glands.
1% incidence in autopsy studies; much less commonly symptomatic.
Males > Females; Usually 30-60 y/o.
75% single stones; 5% bilateral.
Sxs: Swelling, discomfort surrounding affected gland. May wax and wane.


Sialadenitis

Enlarged, inflamed gland; May have systemic symptoms.
More elderly, dehydrated, debilitated patients.
May be secondary to obstructing stone, bacterial (MC S. aureus), viral, post XRT.

Important complications:
- Secondarily infected as a result of ductal obstruction/stasis (especially in elderly patients).
- Erosion of calculus through duct wall with chronic fibrotic reaction.
- Poorly functioning gland secondary to chronic inflammation.

Orbital blow out fracture

Findings

Figure 1: The x-ray demonstrates a fracture of the right orbital floor and an air-fluid level in the right maxillary sinus suspicious for hematoma.
Figure 2: Coronal CT image demonstrates a fracture of the left orbital floor along with herniation of the orbital fat. Air-fluid level in the left maxillary sinus containing high attenuation is consistent with hematoma.


Diagnosis: Orbital blow out fracture


An orbital blow-out fracture is a fracture of the orbital floor caused by blunt trauma to the orbit. Blow-out fractures are usually caused by round or oval object with a diameter slightly larger than the orbital diameter such as a baseball, snowball, tennis ball or fist. The mechanism of fracture is controversial. The two most accepted theories are: 1) The "retropulsion" theory which proposes the fracture is a result of a sudden increase in intraorbital pressure when the globe is pushed posteriorly. 2) The "buckling" theory states that the fracture is secondary to the force causing the orbital rim to buckle and transmitting the force into the orbital bones.

One may expect medial wall fractures to be more common than orbital floor fractures as the medial wall is thinner; however, the reverse is true. Proponents of the "retropulsion" theory attribute this to the honeycomb structure of the ethmoid air cell septae, which support the lamina papyracea, thus allowing it to withstand the sudden rise in intraorbital hydraulic pressure better than the orbital floor. Proponents of the “buckling” theory propose that the orbital floor is particularly vulnerable as the infraorbital canal further weakens the floor’s already delicate bony structure.

Routine facial views obtained should include the Caldwell and Waters view. The Caldwell projection is used to evaluate the lateral orbital wall and ethmoid bone, while the Waters view is useful for visualizing the inferior orbital wall and maxillary sinuses. The teardrop sign is secondary to opacification of the upper maxillary sinus from herniated orbital fat.

CT has become the modality of choice to evaluate orbital fractures. Herniation of orbital fat, the inferior rectus muscle, and the inferior oblique muscle may occur and herniated extraocular muscles entrapped between the fragmented bone segments may lead to diplopia. Edema and hemorrhage from the trauma can also cause diplopia; however this should resolve in a few days in the absence of entrapment. Immediate surgical intervention may be required in cases of entrapped extraocular muscles or acute enopthalmos. Chronic enopthalmos may also develop in fractures with extensive orbital fat herniation.

Malignant peripheral nerve sheath tumor (Malignant melanotic schwannoma)

Findings

Figure 1 : Axial T1 MR image demonstrates a smooth fusiform right paraspinal mass of inhomogeneous intermediate signal intensity without skeletal involvement.
Figure 2: Axial T1 fat-suppressed MR image demonstrates intermediate to relatively high signal intensity of the paraspinal mass.
Figure 3 and Figure 4: Axial and coronal T1 MR images with gadolinium demonstrate heterogeneous enhancement of the paraspinal mass. The coronal image demonstrates close association of the mass with the thoracic nerve roots.


Diagnosis: Malignant peripheral nerve sheath tumor (Malignant melanotic schwannoma)


The term malignant schwannoma, including the malignant melanotic subtype, is no longer used. Malignant peripheral nerve sheath tumor (MPNST) is the accepted nomenclature by the World Health Organization Committee used to describe a spindle cell sarcoma arising from a nerve or neurofibroma or demonstrating nervous tissue differentiation. These highly aggressive neoplasms can locally infiltrate as well as metastasize, most commonly to the lungs. Neurofibromas may undergo transformation to MPNST, which may or may not be associated with neurofibromatosis Type 1 (NF-1). Overall there is a 4% chance of malignant transformation to MPNST in NF-1, and any rapid change in size of a previously stable neurofibroma should warrant immediate biopsy. MPNST occur in men and women with equal frequency except in cases of NF-1, where men are four times more likely to be affected than women.

MPNST usually involve major nerve trunks, typically the sciatic nerve, brachial plexus, and sacral plexus. Patients present with pain and neurological symptoms more often than do patients with benign PNST. Rarely, the alimentary tract, subcutaneous tissues, parotid glands, and the orbits can also be involved. In extremely rare cases, these tumors have been found in the cerebellopontine angles along the cranial nerves.

MR is the diagnostic modality of choice for characterizing neurogenic tumors. However, distinguishing MPNST from neurofibromas, schwannomas or other benign lesions may at times be challenging, particularly in the absence of the “target,” fascicular,” or “split-fat” signs that typically reflect a benign etiology. MPNST are usually fusiform in shape, larger than 5 cm, and appear irregular and heterogeneous depending on the degree of cystic degeneration, hemorrhage, necrosis, and cellularity. They may be isointense or slightly hyperintense compared to muscle on T1WI. The signal intensity and heterogeneity are markedly greater on T2WI, and enhancement is seen after IV contrast. Other helpful clues in determining malignancy are identifying tumor invasion into surrounding adipose and adjacent structures, as well as associated bone and soft tissue edema. The extent of cortical bone involvement is better assessed with CT. It has also been reported that on Gallium-67 citrate imaging the degree of uptake by MPNST is greater than that for benign lesions, which may prove helpful in equivocal cases.

Management of MPNST requires complete surgical resection if possible. Post-operative radiation and chemotherapy are also necessary due to the high risk of recurrence, regardless of complete or incomplete tumor resection. Even with aggressive therapy, about 50% of patients have local recurrence. The reported 5-year survival rate for patients with MPNST but without NF-1 is 50%, whereas for patients with both MPNST and NF-1 it decreases to approximately 10%.

Angioedema of neck

Findings

CT of the neck one month prior revealed asymmetric thickening of the pharyngeal mucosal space and the submucosal larynx on the left. Current CT of the neck shows asymmetric, mass like soft tissue in the right parapharyngeal space and associated structures with resolution of findings on the L side.

Differential diagnosis:
- Angioedema
- Peritonsillar edema/abscess
- Pharyngeal carcinoma
- Lymphoma
- Facial lymphedema

Additional clinical history: Patient is on Angiotensin converting enzyme (ACE) inhibitor therapy.


Diagnosis: Angioedema of neck


Key points

Angioedema is localized subdermal or mucosal swelling due to postcapillary venule inflammation.
Angioedema is mediated by vasoactive substances (like histamine) which locally dilates vessels and causes local vascular leaking.
Angioedema is classified as hereditary, acquired, allergic, secondary to medication or idiopathic.
Examples of medications causing angioedema are radiocontrast agents, ACE inhibitors, Aspirin and NSAIDs amongst other agents.
Angioedema can occur anywhere in the body but often involves the head and neck, including face, lips, tongue, and larynx and the GI tract.
Angioedema can cause acute airway compromise and death.
Radiologist may encounter angioedema when imaging the head and neck or the small bowel, or may encounter it related to contrast reactions.
ACE inhibitors cause angioedema in 0.1-0.5% of patients who use them, and is reported to be the leading cause of acute angioedema in the emergency department with 20% of cases being life-threatening.
Radiographic findings in the head and neck include swelling of the epiglottis, aryepiglottic folds, and prevertebral and submental soft tissue.
Angioedema is a cause of unexplained acute or chronic abdominal pain.
Abdominal CT findings included thickening of small bowel wall and mucosal enhancement.

Pott’s puffy tumor

Findings

There is loculated fluid within the right frontal sinus with thick, nodular peripheral enhancement. This is associated with cortical disruption of both the outer and inner table table of the right frontal bone. There is mild thickening and asymmetric enhancement of the subjacent dura without discrete intracranial fluid collection is seen. Extracranially the right frontal sinus is contiguous with a scalp fluid collection, also demonstrating peripheral enhancement with mild induration in the adjacent subcutaneous tissues.


Diagnosis: Pott’s puffy tumor (frontal sinusitis, osteomyelitis, abscess)


Key points

First described by Sir Percival Pott in 1760.
A complication (triad) of bacterial frontal sinusitis with frontal bone osteomyelitis and resultant overlying scalp abscess.
Occasionally may be complicated by intracranial infection: Subdural or epidural abscess, even brain abscess.
Age: 10-20 years.
Pathogens: H.influenza, Klebsiella, Strep, Staph.
Condition now exceedingly rare in the post-antibiotic era.


Radiologic overview

Frontal sinus opacification, destruction of inner and/or outer table of bone, soft tissue mass/fluid collection (abscess) in scalp tissues or in extra-axial space.

MRI:
- T2: Sinus hyperintensity.
- T1: Disruption of inner/outer tables of frontal bone.
- T1+C:
Rim-enhancing fluid collection in superficial scalp.
Key in characterizing intracranial involvement, i.e., underlying dural enhancement / enhancing extra-axial collection.

Surgical emergencies include:
- Epidural abscess – lentiform shape, cannot cross sutures, may cross falx.
- Subdural abscess – crescentic shape, may cross sutures, cannot cross falx

Dyke-Davidoff-Masson syndrome

Findings

Marked right sided cystic encephalomalacia with ex-vacuo dilation of the right lateral ventricle. Essentially entire R ICA distribution. Asymmetric thickening of the right calvarium and hypertrophy of the right frontal sinus.

Associated differential diagnosis: Increased skull thickness
- Generalized:
Cerebral atrophy ie following shunt insertion for hydrocephalus.
Chronic severe anemia (e.g. thalassemia, Sickle cell disease.)
Chronic dilantin ingestion.
Engelmann disease
Hyperparathyroidism
Acromegaly
Osteopetrosis (mainly skull base)

- Focal:
Dyke-Davidoff syndrome
Fibrous dysplasia
Hyperostosis frontalis interna
Meningioma
Metastases


Diagnosis: Dyke-Davidoff-Masson syndrome


Discussion

Cerebral hemiatrophy or Dyke-Davidoff-Masson syndrome is a condition characterized by seizures, facial asymmetry, contralateral hemiplegia or hemiparesis, and mental retardation. These findings are due to cerebral injury that may occur early in life or in utero. Typically the condition is due to middle cerebral artery stroke in utero. However congenital infection and trauma are other etiological factors. Patients may present with a range of clinical manifestations. In some patients such as the case presented, the condition is asymptomatic and is often picked up as an incidental finding.

The radiological features of Dyke-Davidoff-Masson syndrome are unilateral loss of cerebral volume and associated compensatory bone alterations in the calvarium, like thickening, hyperpneumatization of the paranasal sinuses and mastoid cells and elevation of the petrous ridge. Classical findings of the syndrome are present in variable degrees according to the extent of the brain injury. Plain radiographs of the skull are useful in demonstrating diploic space thickening and hyperpneumatization of the paranasal sinuses. CT demonstrates to better effect the osseous changes with a more accurate estimation of both diploic space widening and paranasal sinus changes.

The magnetic resonance (MR) findings of Dyke-Davidoff-Masson syndrome are similar to many of the CT findings encompassing a unilaterally small cerebral hemisphere together with ipsilateral diploic calvarial expansion, elevation of the petrous bone and orbital roof, and hypoplasia/atrophy of the cerebral peduncle.

The pathologic alterations of cerebral tissue and the brainstem are reflected in detail on MR studies. MR findings in addition to the primary vascular insult may include prominence of the cortical sulci and perimesencephalic cistern but some patients demonstrate absence of such generalized sulcal prominence. Although computed tomography (CT) and MR are complimentary, it is felt that MR represents the imaging procedure of choice with respect to the assessment of the etiology and extent of cerebral parenchymal involvement in patients presenting with a clinical combination of congenital or early onset of seizures, hemiparesis/plegia, and/or craniofacial asymmetry.

Subacute combined degeneration of the spinal cord

Findings

Axial T2 images of cervical cord shows increased T2 signal in both dorsal columns in the form of "inverted rabbit ears". Sagittal T2 images confirm increased T2 signal in the dorsal aspect of the cord corresponding to the location of the dorsal columns. Sagittal T1 with contrast shows no abnormal enhancement of the dorsal columns.

Differential Diagnosis:
- Infectious myelitis such as HIV
- Post infectious myelitis (ADEM)
- Multiple sclerosis
- Copper deficiency

Pathologic correlation: Laboratory testing revealed macrocytic anemia with low serum B12 and normal folate levels. No Intrinsic factor antibodies. Patient clinically improved with subsequent B12 therapy.


Diagnosis: Subacute combined degeneration of the spinal cord from Vitamin B12 deficiency


Discussion

Subacute combined degeneration (SCD) is a reversible cervical myelopathy caused by B12 (cobalamin) deficiency. Findings occur predominantly within the dorsal columns of the lower cervical and upper thoracic spinal cord. The corticospinal and lateral spinothalamic tracts are less commonly involved. B12 deficiency results in macrocytic anemia and neuropsychiatric manifestations including paresthesias, alterations in proprioception, myelopathy, cognitive and behavioral changes.

B12 is a required coenzyme for DNA synthesis and myelination of neurons. Deficiency of the vitamin causes accumulation of methylmalonic acid which is myelin toxic, leading to the neurological manifestations of SCD.

B12 deficiency can be multifactorial although pernicious anemia is the most common etiology. Other causes include malabsorption syndromes, chronic pancreatitis, bacterial over growth, large segment ileal resection, tropical sprue, Dyphillobothrium latum (fish tapeworm) infestation, strict vegetarian diet and rarely from anesthetics.

Nitrous oxide (NO), historically known as "laughing gas" due to the euphoric effects incurred by inhaling the chemical, is found in a popular recreational drug known as "Whippets". NO is also used as an anesthetic agent for surgical procedures. NO has the propensity to inactivate B12 by oxidation precipitating subacute combined degeneration in patients with low or borderline B12 stores.


Imaging

Radiological diagnosis of cervical myelopathy is based on the characteristic symmetrical T2 hyperintensity involving the dorsal columns seen as an " inverted V" or "inverted rabbit ears" on the axial plane. Variable contrast enhancement has been described. Although the findings are typical, SCD is a clinical diagnosis.