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Bell's palsy is a form of facial paralysis resulting from a dysfunction of the cranial nerve VII (the facial nerve) causing an inability to control facial muscles on the affected side. Often the eye in the affected side cannot be closed. The eye must be protected from drying up, or the cornea may be permanently damaged, resulting in impaired vision. In some cases denture wearers experience some discomfort. The common presentation of this condition is a rapid onset of partial or complete paralysis that often occurs overnight. In rare cases (<1%), it can occur on both sides resulting in total facial paralysis. Bell's palsy is defined as a one-sided facial nerve paralysis of unknown cause. Several other conditions can also cause facial paralysis, e.g., brain tumor, stroke, myasthenia gravis, and Lyme disease; however, if no specific cause can be identified, the condition is known as Bell's palsy. It is thought that an inflammatory condition leads to swelling of the facial nerve. The nerve travels through the skull in a narrow bone canal beneath the ear. Nerve swelling and compression in the narrow bone canal are thought to lead to nerve inhibition or damage. Typically, the condition gets better on its own with most achieving normal or near-normal function. Corticosteroids have been found to improve outcomes, when used early, while anti-viral medications are of questionable benefit. Many show signs of improvement as early as 10 days after the onset, even without treatment. Bell's palsy is the most common acute disease involving a single nerve and is the most common cause of acute facial nerve paralysis (>80%). It is named after Scottish anatomist and Edinburgh graduate Charles Bell (1774–1842), who first described it. It is more common in adults than children. ==Signs and symptoms== Bell's palsy is characterized by a one-sided facial droop that comes on within 72 hours.〔 The facial nerve controls a number of functions, such as blinking and closing the eyes, smiling, frowning, lacrimation, salivation, flaring nostrils and raising eyebrows. It also carries taste sensations from the anterior two-thirds of the tongue, via the chorda tympani nerve (a branch of the facial nerve). Because of this, people with Bell's palsy may present with loss of taste sensation in the anterior 2/3 of the tongue on the affected side. Although the facial nerve innervates the stapedial muscles of the middle ear (via the tympanic branch), sound sensitivity and dysacusis are hardly ever clinically evident.〔 Although defined as a mononeuritis (involving only one nerve), people diagnosed with Bell’s palsy may have "myriad neurological symptoms" including "facial tingling, moderate or severe headache/neck pain, memory problems, balance problems, ipsilateral limb paresthesias, ipsilateral limb weakness, and a sense of clumsiness" that are "unexplained by facial nerve dysfunction".〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bell's palsy」の詳細全文を読む スポンサード リンク
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