356 THE EAR (2) in which they have invaded the subarachnoid space. The dura mater, arachnoid and pia mater are all resistant to infection. In very severe cases the superficial layers of the brain itself are infected and the condition is one of meningo-encephalitis. Circumscribed Serous Meningitis. This may occur in the middle cranial fossa associated with petrositis or Gradenigo's syndrome (p. 348). When found in the posterior cranial fossa—Bardny's syndrome—it may follow an otitis media or occasionally a radical mastoid operation. The patient com- plains of giddiness, occipital headache, deafness and tinnitus, and on exami- nation there is nystagmus on looking towards the healthy side, and falling and past-pointing to the diseased side. There may or may not be optic neuritis. On lumbar puncture the cerebrospinal fluid is normal. There may be spontaneous disappearance of the symptoms after a feeling that some- thing has burst in the back of the head. Treatment is by antibiotics. Diffuse Purulent Meningitis. The first sign of meningitis in a case of laby- rinthitis is slight torpidity and confusion without irritability, but with evi- dence of premonition regarding an eventual recovery. This stage may have been recognized by the patient's friends. Males are affected in 75 per cent of cases. The early features associated with this disease are headache, neck stiffness and loss of the superficial abdominal reflexes. Should these be present in combination with a diminution of the chlorides and sugar in the cerebrospinal fluid the diagnosis of diffuse purulent meningitis is no longer in doubt. The temperature in the early stage is usually between 38 and 38-5 °C and the patient suffers from frontal or occipital headache, with tenderness and rigidity of the muscles at the back of the neck. This is most easily tested by lifting the patient's head off the pillow or by pressure over the atlanto-occipital membrane. In the earlier stages of meningitis arising from extradural abscess in the posterior cranial fossa the symptoms are not definite. There may be an initial rigor. Pain is localized at first to the side or back of the head, but later becomes general. Accompanying the headache are fever, restlessness, and marked irritability of temper; vomiting is often present and the tongue is heavily coated, and the teeth covered by sordes. The patient frequently lies with his knees drawn up and head turned away from the light (photo- phobia). Periods of excitement come on at times, during which he may cry out or talk incoherently. In meningitis the strength of the cry gradually increases, whereas in brain abscess the cry is strongest at first and tails off as the patient relapses into a semi-comatose condition. Delirium is common in children and convulsions are not infrequent. Herpes labialis may be present. Occasionally severe pain in the back is complained of. The reflexes are increased and, especially in children, the abdomen is retracted. An in- ability to extend the knee when the thigh is flexed (Kernig's sign) is generally present. The temperature rises sharply and remains elevated (39-5 to 40 °C) and towards the end may rise to 41 or 42 °C. The pulse, at first strong and slow considering the presence of fever, soon becomes weak and fast, and the blood pressure becomes very low. Blood examination usually shows a leucocytosis of about 20 x 109/1. In meningitis arising in the middle cranial fossa, headache and fever may be the only symptoms, or the case may closely resemble one of temporal lobe abscess.