Acoustic Neuroma

The term "acoustic neuroma" is actually a misnomer since the tumor never arises from the acoustic division of the vestibulocochlear nerve (cranial nerve VIII) and the tumor is not a neuroma but a schwannoma.

Acoustic neuroma (or Vestibular Schwannoma) is a benign primary intracranial tumor, or brain tumor, of the myelin forming cells called "Schwann cells" (Schwannoma) of the 8th cranial nerve -also known as the acoustic nerve, (or more properly the vestibulocochlear nerve).

The vast majority (95%) of these tumors are sporadic, meaning they are not passed on through genes. Sporatic tumors occur in only one ear, and there are no known risk factors. Rarely these tumors are associated with a genetic disease called Neurofibromatosis Type II. Patients with Neurofibromatosis develop tumors at a younger age, usually have tumors on both sides and also have other manifestations, including benign tumors of the brain and dura (the covering of the brain).

Vestibular Schwannomas are generally slow growing (less than 3 millimeters per year) and may not grow at all if followed over time. However, tumor growth is not predictable, and some tumors grow more rapidly. When tumors are small they may give no symptoms or very subtle symptoms, such as a slight hearing loss or a noise in the ear (tinnitus). When tumors grow, they begin to cause injury to the hearing nerve and balance nerve, by compressing them. Patients may experience severe hearing loss (either suddenly or progressively over a period of years) or balance problems. Large tumors may compress the brainstem and result in headaches and other symptoms of increased intracranial pressure. Symptoms don't correlate well with size. Some patients with very small tumors may have obvious symptoms and likewise, some patients with large tumors may have no symptoms at all.

The diagnosis of Vestibular Schwannoma is made by history, hearing tests, and MRI scan. Gadolinium is a special contrast agent used during the MRI to allow visualization of the tumors. With good technique, MRI will show tumors as small as 2-4 millimeters.

Tripod Fracture

The zygomatic complex, also known as the trimalar complex, is a facial bone commonly injured in low-velocity trauma. Lateral trauma will sometimes produce an isolated zygomatic arch fracture; however, more severe force can fracture the entire zygomatic complex.

Although commonly referred to as a "tripod" fracture, this name is a misnomer: a zygomatic complex fracture constitutes four discrete fractures.

The components of this fracture are

(1) the zygomatic arch,

(2) the orbital rim,

(3) the frontozygomatic buttress, and

(4) the zygomatico-maxillary buttress.

Skull Base Surgery

Although in widespread use, the term "skull base surgery" is a somewhat of a misnomer. Only a minority of such procedures is undertaken to expose lesions actually located primarily within the skull base. The majority of procedures is conducted to expose deep-seated intracranial lesions situated either adjacent to the brainstem (eg, midbrain, pons, or medulla) or beneath the cerebral cortex.

Previously, many such tumors were approached via simple openings in the calvaria, which requires vigorous and often injurious degrees of brain retraction.

The fundamental principle in transbasal craniotomy is removal of the skull base bone in order to minimize the need for brain retraction. Although current techniques represent a major enhancement in our ability to control inaccessible tumors while minimizing morbidity, they are not panaceas. For example, experience has shown that these procedures are far more suitable for benign lesions (eg, meningiomas, schwannomas, and paragangliomas) and even for low-grade malignant growths (eg, chordomas and chondrosarcomas) than they are for high-grade malignant lesions (eg, squamous cell carcinoma, adenocystic carcinoma, and soft tissue sarcomas). Currently, more emphasis is placed on the preservation of function, especially cranial nerves, than on the necessity for radical resection in every case. The value of neurophysiologic nerve monitoring for motor nerves within the surgical field has become well established. In the developmental years of skull base surgery, two-stage procedures were common. More recently, single-stage procedures have become preferred in most centers, even for tumors with sizable intra- and extracranial components, as well as those involving multiple cranial fossae. Computerized imaging modalities provide localizing information that guides the surgeon around vital structures and helps to enable thorough tumor removal.

Malignant Otitis Externa

The term is misnomer because this condition is termed as malignant otitis externa because of itspropensity to cause complications and death.

This is an inflammatory disorder involving the external auditory canal,hence the term malignant otitis external is a misnomer. It is caused by Pseudomonas group oforganisms.

Commonly this condition affects elderly diabetics. It is very rare in children.

Cholesteatoma

The term cholesteatoma is actually a misnomer since the lesion is not a neoplasm and does not contain cholesterol.

The primary lesion in the differential diagnosis with cholesterol granuloma is cholesteatoma.