This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
Meningeal hemorrhage may be either subarachnoid or subdural. If the hemorrhage has not been violent, it spreads out under the arachnoid in the subarachnoid space. If, however, the blood has escaped with considerable force, it tears its way through the arachnoid and spreads in the subdural, as well as through the subarachnoid space. The origin of this form of hemorrhage is the vessels of the pia mater. The arachnoid does not give rise to hemorrhages, neither does the inner surface of the dura, unless it has previously been the seat of pachymeningitis interna.
The hemorrhage is the result either of injury or disease. In children it is usually due to injury; in adults to either injury or disease. These hemorrhages are most common in infancy and occur in childbirth. They are due apparently to hard, protracted labor or injury done to the child in effecting delivery by forceps, etc., especially in infants born before full term. They are a cause of idiocy and the cerebral palsies of childhood. These hemorrhages in the new-born have been recognized by the convulsions they produce, and successful operations have been performed for their relief (see Harvey Cushing - "Surgical Intervention for the Intracranial Hemorrhages of the New-born" - Am. Jour. Med. Sci., October, 1905). Injuries received later in life from blows on the head often produce subdural or pial hemorrhages, without breaking the overlying bone. They are found either at the site of impact or on the side opposite that on which the blow was received, the latter being produced by contre-coup. When pial hemorrhage occurs from disease, it is usually from rupture of an aneurism of one of the vessels of the pia mater. If it does not break through the arachnoid into the subdural space, it may spread over a considerable portion of the cerebral cortex, especially filling the sulci. Unless the quantity is quite large, so that it interferes with the motor area, hemiplegia will not occur. Convulsions may occasionally occur from irritation of the cortex. Blood in the subdural space may travel along the base of the brain and into the sheath of the optic nerve.
Fig. 28. - Base of brain, showing exit of cranial nerves.