ganglion

1. a mass of nervous tissue containing nerve cells and SYNAPSES . Chains of ganglia are situated on each side of the SPINAL CORD while other ganglia are sited near to or in the appropriate organs. Within the CENTRAL NERVOUS SYSTEM , some well-defined masses of nerve cells are called ganglia, e.g. basal ganglia (see BASAL GANGLION ). 2. a BENIGN swelling that often forms in the sheath of a TENDON and is fluid-filled. It occurs particularly at the wrist and may disappear quite suddenly.