Meningoencephalitis (; from Ancient Greek: μῆνιγξ, romanized: meninx, lit. membrane; Ancient Greek: ἐγκέφαλος, romanized: enképhalos, lit. brain; and the medical suffix -itis, "inflammation"), also known as herpes meningoencephalitis, is a medical condition that simultaneously resembles both meningitis, which is an infection or inflammation of the meninges, and encephalitis, which is an infection or inflammation of the brain. Signs and symptoms
Signs of meningoencephalitis include unusual behavior, personality changes, and thinking problems.Symptoms may include headache, fever, pain in neck movement, light sensitivity, and seizure. Causes
Causative organisms include protozoans, viral and bacterial pathogens.Specific types include:

Bacterial
Veterinarians have observed meningoencephalitis in animals infected with listeriosis, caused by the pathogenic bacteria L. monocytogenes. Meningitis and encephalitis already present in the brain or spinal cord of an animal may form simultaneously into meningeoencephalitis. The bacterium commonly targets the sensitive structures of the brain stem. L. monocytogenes meningoencephalitis has been documented to significantly increase the number of cytokines, such as IL-1β, IL-12, IL-15, leading to toxic effects on the brain.Meningoencephalitis may be one of the severe complications of diseases originating from several Rickettsia species, such as Rickettsia rickettsii (agent of Rocky Mountain spotted fever (RMSF)), Rickettsia conorii, Rickettsia prowazekii (agent of epidemic louse-borne typhus), and Rickettsia africae. It can cause impairments to the cranial nerves, paralysis to the eyes, and sudden hearing loss.
Osteolysis is an active resorption of bone matrix by osteoclasts and can be interpreted as the reverse of ossification. Although osteoclasts are active during the natural formation of healthy bone the term "osteolysis" specifically refers to a pathological process. Osteolysis often occurs in the proximity of a prosthesis that causes either an immunological response or changes in the bones structural load. Osteolysis may also be caused by pathologies like bone tumors, cysts, or chronic inflammation. Joint replacement
While bone resorption is commonly associated with many diseases or joint problems, the term osteolysis generally refers to a problem common to artificial joint replacements such as total hip replacements, total knee replacements and total shoulder replacements. Osteolysis can also be associated with the radiographic changes seen in those with bisphosphonate-related osteonecrosis of the jaw.There are several biological mechanisms which may lead to osteolysis. In total hip replacement, the generally accepted explanation for osteolysis involves wear particles (worn off the contact surface of the artificial ball and socket joint). As the body attempts to clean up these wear particles (typically consisting of plastic or metal), it triggers an autoimmune reaction which causes resorption of living bone tissue. Osteolysis has been reported to occur as early as 12 months after implantation and is usually progressive. This may require a revision surgery (replacement of the prosthesis).Although osteolysis itself is clinically asymptomatic, it can lead to implant loosening or bone breakage, which in turn causes serious medical problems.