High Pressure Neurological Syndrome: A syndrome related to increased atmospheric pressure and characterized by tremors, nausea, dizziness, decreased motor and mental performance, and SEIZURES. This condition may occur in those who dive deeply (c. 1000 ft) usually while breathing a mixture of oxygen and helium. The condition is associated with a neuroexcitatory effect of helium.Mephenesin: A centrally acting muscle relaxant with a short duration of action.Paraneoplastic Syndromes, Nervous System: Degenerative or inflammatory conditions affecting the central or peripheral nervous system that develop in association with a systemic neoplasm without direct invasion by tumor. They may be associated with circulating antibodies that react with the affected neural tissue. (Intern Med 1996 Dec;35(12):925-9)Paraneoplastic Polyneuropathy: A diffuse or multifocal peripheral neuropathy related to the remote effects of a neoplasm, most often carcinoma or lymphoma. Pathologically, there are inflammatory changes in peripheral nerves. The most common clinical presentation is a symmetric distal mixed sensorimotor polyneuropathy. (Adams et al., Principles of Neurology, 6th ed, p1334)Paraneoplastic Cerebellar Degeneration: Cerebellar degeneration associated with a remote neoplasm. Clinical manifestations include progressive limb and GAIT ATAXIA; DYSARTHRIA; and NYSTAGMUS, PATHOLOGIC. The histologic type of the associated neoplasm is usually carcinoma or lymphoma. Pathologically the cerebellar cortex and subcortical nuclei demonstrate diffuse degenerative changes. Anti-Purkinje cell antibodies (anti-Yo) are found in the serum of approximately 50% of affected individuals. (Adams et al., Principles of Neurology, 6th ed, p686)Syndrome: A characteristic symptom complex.Stiff-Person Syndrome: A condition characterized by persistent spasms (SPASM) involving multiple muscles, primarily in the lower limbs and trunk. The illness tends to occur in the fourth to sixth decade of life, presenting with intermittent spasms that become continuous. Minor sensory stimuli, such as noise and light touch, precipitate severe spasms. Spasms do not occur during sleep and only rarely involve cranial muscles. Respiration may become impaired in advanced cases. (Adams et al., Principles of Neurology, 6th ed, p1492; Neurology 1998 Jul;51(1):85-93)Nervous System Diseases: Diseases of the central and peripheral nervous system. This includes disorders of the brain, spinal cord, cranial nerves, peripheral nerves, nerve roots, autonomic nervous system, neuromuscular junction, and muscle.Paraneoplastic Syndromes: In patients with neoplastic diseases a wide variety of clinical pictures which are indirect and usually remote effects produced by tumor cell metabolites or other products.