Current records may significantly underestimate the frequency of strong (EF2-EF3) and violent (EF4-EF5) tornadoes, as damage-based intensity estimates are limited to structures and vegetation that a tornado impacts. A tornado may be much stronger than its damage-based rating indicates if its strongest winds occur away from suitable damage indicators, such as in an open field. Outside Tornado Alley, and North America in general, violent tornadoes are extremely rare. This is apparently mostly due to the lesser number of tornadoes overall, as research shows that tornado intensity distributions are fairly similar worldwide. A few significant tornadoes occur annually in Europe, Asia, southern Africa, and southeastern South America. Climatology
The United States has the most tornadoes of any country, nearly four times more than estimated in all of Europe, excluding waterspouts. This is mostly due to the unique geography of the continent. North America is a large continent that extends from the tropics north into arctic areas, and has no major east–west mountain range to block air flow between these two areas. In the middle latitudes, where most tornadoes of the world occur, the Rocky Mountains block moisture and buckle the atmospheric flow, forcing drier air at mid-levels of the troposphere due to downsloped winds, and causing the formation of a low pressure area downwind to the east of the mountains. Increased westerly flow off the Rockies force the formation of a dry line when the flow aloft is strong, while the Gulf of Mexico fuels abundant low-level moisture in the southerly flow to its east.
Melkersson–Rosenthal syndrome is a rare neurological disorder characterized by recurring facial paralysis, swelling of the face and lips (usually the upper lip: cheilitis granulomatosis) and the development of folds and furrows in the tongue (fissured tongue). : 799  Onset is in childhood or early adolescence. After recurrent attacks (ranging from days to years in between), swelling may persist and increase, eventually becoming permanent. The lip may become hard, cracked, and fissured with a reddish-brown discoloration. The cause of Melkersson–Rosenthal syndrome is unknown, but there may be a genetic predisposition. It has been noted to be especially prevalent among certain ethnic groups in Bolivia. It can be symptomatic of Crohns disease or sarcoidosis. Approximately 400 cases have been reported worldwide. Cause
Not to be confused with Rosenthal syndrome a.k.a. hemophilia C which is caused by clotting factor XI deficiency. Only genetic causation is established as it is associated with twins and family members. Diagnosis
Diagnosis is mainly based on clinical features. However, biopsy has been useful in diagnosis as well as in differentiating between the different types of the disease. Treatment
Treatment is symptomatic and may include nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids to reduce swelling, antibiotics and immunosuppressants. Surgery may be indicated to relieve pressure on the facial nerves and reduce swelling, but its efficacy is uncertain. Massage and electrical stimulation may also be prescribed. Prognosis
Melkersson–Rosenthal syndrome may recur intermittently after its first appearance. It can become a chronic disorder. Follow-up care should exclude the development of Crohns disease or sarcoidosis.