Structure
The human ear consists of three parts—the outer ear, middle ear and inner ear. The ear canal of the outer ear is separated from the air-filled tympanic cavity of the middle ear by the eardrum. The middle ear contains the three small bones—the ossicles—involved in the transmission of sound, and is connected to the throat at the nasopharynx, via the pharyngeal opening of the Eustachian tube. The inner ear contains the otolith organs—the utricle and saccule—and the semicircular canals belonging to the vestibular system, as well as the cochlea of the auditory system. Outer ear
The outer ear is the external portion of the ear and includes the fleshy visible pinna (also called the auricle), the ear canal, and the outer layer of the eardrum (also called the tympanic membrane).The pinna consists of the curving outer rim called the helix, the inner curved rim called the antihelix, and opens into the ear canal. The tragus protrudes and partially obscures the ear canal, as does the facing antitragus. The hollow region in front of the ear canal is called the concha. The ear canal stretches for about 1 inch (2.5 cm). The first part of the canal is surrounded by cartilage, while the second part near the eardrum is surrounded by bone. This bony part is known as the auditory bulla and is formed by the tympanic part of the temporal bone. The skin surrounding the ear canal contains ceruminous and sebaceous glands that produce protective ear wax.
Antibodies against voltage-gated calcium channels can be identified in 85% of people with EMG-confirmed LEMS. Once LEMS is diagnosed, investigations such as a CT scan of the chest are usually performed to identify any possible underlying lung tumors. Around 50–60% of these are discovered immediately after the diagnosis of LEMS. The remainder is diagnosed later, but usually within two years and typically within four years. As a result, scans are typically repeated every six months for the first two years after diagnosis. While CT of the lungs is usually adequate, a positron emission tomography scan of the body may also be performed to search for an occult tumour, particularly of the lung. Treatment
If LEMS is caused by an underlying cancer, treatment of the cancer usually leads to resolution of the symptoms. Treatment usually consists of chemotherapy, with radiation therapy in those with limited disease. Immunosuppression
Some evidence supports the use of intravenous immunoglobulin (IVIG). Immune suppression tends to be less effective than in other autoimmune diseases. Prednisolone (a glucocorticoid or steroid) suppresses the immune response, and the steroid-sparing agent azathioprine may replace it once therapeutic effect has been achieved. IVIG may be used with a degree of effectiveness. Plasma exchange (or plasmapheresis), the removal of plasma proteins such as antibodies and replacement with normal plasma, may provide improvement in acute severe weakness. Again, plasma exchange is less effective than in other related conditions such as myasthenia gravis, and additional immunosuppressive medication is often needed.