Fourth cranial nerve palsy or trochlear nerve palsy, is a condition affecting cranial nerve 4 (IV), the trochlear nerve, which is one of the cranial nerves. It causes weakness or paralysis of the superior oblique muscle that it innervates. This condition often causes vertical  or near vertical double vision as the weakened muscle prevents the eyes from moving in the same direction together. Because the trochlear nerve is the thinnest and has the longest intracranial course of the cranial nerves, it is particularly vulnerable to traumatic injury. To compensate for the double-vision resulting from the weakness of the superior oblique, patients characteristically tilt their head down and to the side opposite the affected muscle. When present at birth, it is known as congenital fourth nerve palsy. See also
Harada–Ito procedure

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Acute cutaneous lupus erythematosus is a cutaneous condition characterized by a bilateral malar rash (also known as a "butterfly rash") and lesions that tend to be transient, and that follow sun exposure. The acute form is distinct from chronic and subacute cutaneous lupus erythematosus, which may have different types of skin lesions. Cutaneous lupus erythematosus is associated with both lupus erythematosus-specific lesions and cutaneous manifestations that are not specific to lupus erythematosus, such as oral ulcers and urticaria. Because of the diagnostic criteria used to diagnose systemic lupus erythematosus, a patient with only cutaneous manifestations may be diagnosed with the systemic form of the disease. Forms
Acute cutaneous lupus erythematosus can be either localized or generalized. Localized form
The localized form of the disease is most commonly associated with the malar rash and normally develops in a patients twenties. The localized form occurs only above the patients neck and is not associated with rashes in other parts of the body. Generalized form
Generalized acute cutaneous lupus erythematosus includes skin below the patients neck and is described as a macropapular rash or photosensitive lupus dermatitis. Symptoms include similar erythematic lesions as seen in the localized form, but forms a symmetrical rash and can be mistaken for a drug rash. See also
Lupus erythematosus
List of cutaneous conditions


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