This section is from the book "A Manual Of Pathology", by Guthrie McConnell. Also available from Amazon: A Manual Of Pathology.
Pachymeningitis, or acute inflammation of the spinal dura mater, is commonly due to neighboring inflammations or to traumatism. In external pachymeningitis there is an exudate, cellular or fibrinous, upon the external surface. Abscesses may form and destroy by pressure the neighboring cord. Internal pachymeningitis is generally secondary to tuberculous or syphilitic disease of the pia and the bones. There is a marked fibrous exudate, with adhesions between the dura and the underlying membranes. Hemorrhagic pachymeningitis is internal, and is similar to the process occurring in the brain. It is characterized by a reddish layer of granulations in which many of the capillaries have ruptured.
Chronic hypertrophic cervical pachymeningitis is a localized thickening of the dura mater in the cervical region. The pia and the arachnoid are also involved. Compression of the cord and secondary degenerations may ensue.
Leptomeningitis, or acute inflammation of the spinal pia and arachnoid, is generally secondary to cerebral meningitis, especially in the epidemic cerebrospinal form. It may be due to local injury or diseases of the bone. There is an exudation, serous, fibrinous, or purulent, upon the inner surface of the dura and the subarachnoid space. The inflammation may be local or involve the greater length of the cord. The tissue of the cord is commonly affected, and extensive round-cell infiltration occurs in the anterior commissure and in the perivascular connective tissue.