The cerebrum, brainstem, cerebellum, and spinal cord are covered by three membranes called meninges. The CNS is protected by the cranium, vertebral column, meninges, cerebrospinal fluid. The meninges, cerebrospinal fluid and skull "smear" the EEG signal, obscuring its intracranial source. Meningitis is an inflammation of the meninges (membranes) of the brain and spinal cord. Arachnoiditis is a broad term denoting inflammation of the meninges and subarachnoid space. It results in inflammation of the meninges (the membranes covering the brain and spinal cord). The mesenchyme above the meninges undergoes intramembranous ossification forming the neurocranium. The spinal cord is surrounded by three layers known as the spinal meninges. Myelomeningocele involves herniation of the meninges as well as the spinal cord through the opening. Neck stiffness is the result of inflamed meninges stretching due to flexion of the spine. A tumor growing from the meninges is referred to as a meningioma. Injuries involving the meninges, can result in a hemorrhage and two types of hematoma. Therefore infection can spread from the scalp to the meninges, which could lead to meningitis. True leaks can form at weak points in the spinal meninges. The dorsal cavity is lined by the three meninges.