Stenosing Tenosynovitis

Stenosing tenosynovitis refers to the adhesion of the tendon to its tendon sheath. MRI and ultrasound may show loculated tendon sheath fluid. Ultrasound may show fixation of the tendon and sheath.

De Quervain disease is a stenosing tenosynovitis of the first dorsal wrist compartment. The extensor pollicis brevis tendons is most commonly involved, but the abductor pollicis longus tendon can also be involved.

Patients with os trigonum syndrome commonly have stenosing tenosynovitis of the flexor hallucis longus tendon.

Special Names of the Ethmoid Air Cells

Agger nasi cells are the most anterior ethmoid air cells and are located within the lacrimal bone. They are located anterior, lateral, and inferior to the frontoethmoidal recess and anterior and above the attachement of the middle turbinate.

Haller cells refer to ethmoid air cells that are located along the inferolateral margin of the orbit and protrude into the maxillary sinus. If they get too big, they can block the drainage pathway of the maxillary sinus.

Ethmoidal bulla refers to the largest ethmoid air cell, located above and behind the infundibulum and hiatus semilunaris. If it gets too big, it can block the drainage pathway of the maxillary sinus and result in the infundibular pattern of sinus disease.

Onodi (sphenoethmoid) cells are the posteriormost ethmoidal air cells that pneumatize into the sphenoid bone superior to the sphenoid sinus. The image shows a left Onodi cell (white arrows) above the left spenoid sinus (pink arrow). The right sphenoid sinus is indicated by the blue arrow. They can be intimately associated with the optic nerve (most common, green arrow) and internal carotid artery (less common). The anterior clinoid process may be pneumatized via Onodi cells (not so in this case). Onodi cells are important in sinus surgery. In a transsphenoidal approach, an Onodi cell can be entered under, resulting in damage the optic nerve or internal carotid artery.

References

Kantarci M, Karasen RM, Alper F, Onbas O, Okur A, Karaman A. Remarkable anatomic variations in paranasal sinus region and their clinical importance. Eur J Radiol. 2004 Jun;50(3):296-302.

Neoplasms Associated with the Neurocutaneous Syndromes

Neurofibromatosis 1

• Low-grade optic nerve pilocytic glioma
• Increased risk of multicentric gliomas
• Neurofibrosarcomas (malignant degeneration of neurofibromas).
• Leukemia, lymphoma
• Medullary thyroid carcinoma
• Pheochromocytoma
• Melanoma
• Wilms tumor

Neurofibromatosis 2: MISME (Multiple Inherited Schwannomas, Meningioma, and Ependymoma)

• Schwannomas: CN 8 > CN V > spinal canal
• Spinal ependymomas
• Meningiomas

von Hippel-Lindau

• Hemangioblastomas: Cerebellum > Retina > Brainstem
• Renal cell carcinoma (more commonly bilateral and smaller than sporadic form)
• Pheochromocytoma

Sturge-Weber

• Angiomas: leptomeninges and skin of the face

Tuberous Sclerosis

• Angiomyolipomas
• Subependymal nodules may degenerate to subependymal giant-cell astrocytomas (SEGA)
• Cardiac rhabdomyomas

Foramen Rotundum and the Vidian Canal

The vidan canal (blue) and foramen rotundum (red) are openings in the greater wing of the sphenoid that connect the pterygopalatine fossa to the middle cranial fossa.

The V2 nerve passes through the foramen rotundum, while the vidian nerve passes through the vidian canal. The vidian nerve is formed by greater superficial and deep petrosal nerves and contains sensory fibers from cranial nerve 7, which supply the soft palate.

Pterygopalatine Fossa

The pterygopalatine fossa (PPF) is a groove between the maxillary bone anteriorly and the pterygoid process posteriorly. Its anteromedial border is the perpendicular plate of the palatine bone.

The pterygopalatine fossa is an important pathway for the spread of neoplastic and infectious processes.

• Laterally: The PPF (red) communicates with the masticator space via the pterygomaxillary fissure (yellow).
• Anteriorly: The PPF communicates with the orbit via the inferior orbital fissure.
• Medially: The PPF communicates with the posterior nasal fossa via the sphenopalatine foramen (purple).
• Posteriorly and superiorly: The PPF communicates with the Meckel cave and cavernous sinus via the foramen rotundum (green).
• Posteriorly and inferiorly: The PPF communicates with the middle cranial fossa via the vidian canal (orange).
• Inferiorly: The PPF communicates with the palate via the greater and lesser palatine foramina.

A tumor that characteristically spreads via the PPF is the juvenile angiofibroma. This tumor may originate in the posterolateral wall of the nasal cavity, where it reaches the PPF through the sphenopalatine foramen. From there, the tumor spreads through the pterygomaxillary fissure into the infratemporal fossa (the part of the masticator space below the level of the zygomatic arch).

The PPF contains the pterygopalatine ganglion, the descending palatine artery (branch of the maxillary artery), V2, and the nerve of the pterygoid canal.

Masses of the PPF include,

• Juvenile angiofibroma
• Invasive tumors
• Meningioma of sphenoid wing or nasal fossa
• Metastasis
• Fracture of pterygoid plates

References

• Neuroradiology: The Requisites. Second Edition.
• Jerry V. Glowniak, Anthony L. Alcantara, Todd Getzen, and Anuj Dhawan. Navigating the Skull Base: An interactive program for learning skull base anatomy. Department of Radiology, Wayne State University School of Medicine.

Tarlov Cyst

Tarlov (perineurial) cysts are outpouchings of the arachnoid and, unlike meningeal cysts, at least part of their wall contains nerve fibers. CSF flows into the space between the endoneurium (extension of the pia mater) and perineurium (extension of the arachnoid mater) under pulsation, and gets trapped via a ball-valve phenomenon. They are most commonly found at the sacral (S2 and S3) nerve roots, where they can be associated with bone erosion, and can rarely cause sciatica.

Differential considerations include meningocele, arachnoid cyst, neurofibroma, and dural ectasia.

References

• IM Tarlov, Spinal perineural and meningeal cysts. J Neurol Neurosurg Psychiatry 33 (1970), pp. 833–843.
• Neuroradiology: The Requisites. Second edition. pp806-807.

Submandibular Gland Sialolithiasis

Calculous disease of the submandibular gland is four times more common than that of the parotid gland. About 70% of submandibular gland calculi are radiopaque.

It is thought that the higher pH and viscosity of the submandibular gland secretions, and the fact that the saliva has to travel uphill to get excreted contribute to the higher incidence of sialolithiasis in the submandibular gland .

The workup for suspected calculous disease of salivary glands (painful glands worsened by chewing) begins with radiographs. If a radiopaque calculus is not found, then CT may be obtained. MR sialography (analogous to MRCP) is >90% accurate for the detection of sialolithiasis.

Sialadenitis is inflammation of the gland and is often associated with ductal ectasia (sialectasis) and most often caused by sialolithiasis. Microabscesses may be seen with sialectasis and/or sialadenitis. Sialodochitis is the inflammation of the ductal system.

Sialadenitis with sialodochitis without other systemic symptoms is referred to as Sjögren type I (also known as Mikulicz disease). When sialadenitis with sialodochitis are associated with a collagen vascular disease, it's referred to as Sjögren type II.

Because people with Sjögren disease are ten times more likely to develop lymphoma, make sure to look closely at the rest of the neck for lymph nodes. The lymphoma may also develop in the salivary glands themselves, so look closely at the glands for signs of lymphoma.

References

Neuroradiology: The Requisites. Second edition. pp 700-703.