Causes of Pituitary Hyperplasia

The pituitary can enlarge physiologically under the following conditions:

• Hypothyroidism
• Pregnancy
• Lactation

Look for a sellar mass that is not separate from the pituitary. In contrast to pituitary adenoma, there is no remodeling of the sella. When in doubt, dynamic contrast-enhanced MRI can resolve the issue. Pituitary hyperplasia will enhance uniformly, while pituitary tumors will have an enhancement pattern different from the rest of the gland.

Torus Mandibularis and Palatinus

Torus mandibularis is an exostosis of the lingual surface of the mandible above the myohyoid line and opposite the bicuspids. They are bilateral in 80% of cases.

When located along the maxilla, the exostoses are referred to torus palatinus (shown).

References

Malin Cesarz, MD and Per-Lennart Westesson, MD, PhD, DDS. University of Rochester Medical Center. Neuroradiology Case of the Week: Case 200.

Multicentric Reticulohistiocytosis

Multicentric reticulohistiocytosis is a rare systemic disorder characterized by cutanenus and mucous nodules and chronic polyarthritis seen most commonly in patients 40 to 50 years of age.

Radiographs reveal marginal erosions principally at the distal interphalangeal joints of the hands that spread centrally. Nodules and cysts are commonly seen at the insertions of the extensor tendons of the fingers.

Differential considerations include:

• Psoriatic arthritis: Asymmetric distribution, periosteal new bone formation, intraarticular ankylosis, and early involvement of the sacroiliac joints are seen in psoriatic arthritis, but are not typical of multicentric reticulohistiocytosis.
• Rheumatoid arthritis: Periarticular osteoporosis, thinning of the articular cartilage, and sparing of the distal interphalangeal joints are seen in rheumatoid arthritis, but not typical of multicentric reticulohistiocytosis.
• Erosive osteoarthritis: Also affects the distal interphalangeal joints of the hands, but the erosions are typically in the central part of the articular surface (gull wing appearance).
• Gout: Also has skin nodules, but the they are asymmetrically distributed in the periarticular soft tissues, in contrast to the cysts and nodules commonly seen at the insertions of the extensor tendons of the fingers in multicentric reticulohistiocytosis. Erosions in gout occur at or near joints with the typical "over-hanging margins."

References

Scutellari PN, Orzincolo C, Trotta F. Case report 375: Multicentric reticulohistiocytosis. Skeletal Radiol. 1986;15(5):394-7.

Contents of the Internal Auditory Canal

• 7.Up = Cranial nerve 7 ("7-up, coke down")
• BB = The Bill bar
• Coke = Cochlear nerve ("7-up, coke down")
• IVN = Inferior vestibular nerve
• SVN = Superior vestibular nerve
• TC = Transverse crest

Central Nervous System Lipomas

Intracranial lipomas are not true tumors, but rather congenital malformations. They are uncommon lesions that tend to involve midline structures, such as the case shown here, which is a lipoma of the tuber cinereum.

80% of central nervous system lipomas are supratentorial, with up to 50% of these occurring at the interhemispheric fissure, 20% suprasellar, and 15% in the pineal region. The 20% that are infratentorial involve the cerebellopontine angle, jugular foramen, and foramen magnum.

On CT, they demonstrate fat attenuation, may have calcifications, and do not enhance. They're hyperintense on T1-weighted (A) images and drop out on fat suppressed images (D). On standard spin echo T2 images, they're hypointense with chemical shift artifact. On fast spin echo T2 images, they are iso- to hyperintense (B) and intermediate signal on proton density images. These lesions do not enhance.

References

Saleem SN, Said AH, Lee DH. Lesions of the hypothalamus: MR imaging diagnostic features. Radiographics. 2007 Jul-Aug;27(4):1087-108.

Ganglioglioma

Gangliogliomas are the most common mixed glioneural tumors of the CNS and most commonly present with seizures. About 40% occur in the temporal lobe, followed by the parietal (30%) and frontal (20%) lobes. They can also be found in the anterior third ventricle, cerebellum, spinal cord, and optic nerves.

Imaging

On CT, they may be hypo (40%) mixed cystic and nodular (30%), isodense (15%), or hyperdense (15%). Mass effect is variable, and there is generally no edema. Up to 50% have calcifications and about 50% demonstrate faint enhancement.

They are hypo- to isointense on T1-weighted images. Solid enhancing components are usually seen (A and B). Calcifications will be hyperintense to gray matter. The solid and cystic parts will be high signal on T2-weighted images (C). No significant peritumoral edema is seen (FLAIR, D).

Variants

The glial portion of a ganglioglioma defines its aggressiveness, and degeneration of the glial component may lead to an anaplastic ganglioglioma.

A desmoplastic infantile ganglioglioma (DIG) is a variant of ganglioglioma that is usually seen in the first 2 years of life. Like the regular ganglioglioma, it is a low-grade tumor with good prognosis. As opposed to the standard ganglioglioma, however, DIGs are more commonly seen in the frontal and parietal lobes. Imaging features may be identical to pilocytic astrocytomas: A large cyst with a peripheral (cortical) enhancing nodule. Some may also have a calcified rim.

References

Neuroradiology: The Requisites. Second ed. pp 136-138.

Wandering Spleen

A wandering spleen is one that is found in a location other than the left upper quadrant. This wandering ability may be due to congenital absence of the ligaments that tether the spleen in place, with the lienorenal ligament being the most important. Hormonally induced laxity of ligaments (e.g., during pregnancy) can also allow the spleen to wander off.

Patients may be asymptomatic, present with chronic abdominal pain (presumably from recurrent torsion), or acute abdominal pain. The dreaded complication of wandering spleen is torsion around its vessels, resulting in infarction.

References

Romero JR, Barksdale EM Jr. Wandering spleen: a rare cause of abdominal pain. Pediatr Emerg Care. 2003 Dec;19(6):412-4