Spontaneous atlanto-axial dislocation is a recognized if rare complication of infections of the pharynx and neck (Bell, 1830;Grisel, 1930;Watson-Jones, 1932) and of childhood rheumatic fever (Coutts, 1934). Werne (1957) (Stammers, 1956) who developed pyramidal signs and sensory changes in the right lower limb and weakness of grip in the left hand as a result of forward dislocation of the atlas on the axis. The neurological abnormalities regressed after the head was extended and a plaster cast was applied. Rand (1944) reported a man probably suffering from ankylosing spondylitis in whom a Brown-Sequard syndrome was associated with atlanto-axial dislocation and Coste, Auquier, and Civatte (1952) described the case of a 37-year-old female said to be suffering from both ankylosing spondylitis and a primary chronic polyarthritis of 5 years' duration in whom atlantoaxial dislocation occurred without neurological complications. Kornblum, Clayton, and Nash (1952) reported two male patients with ankylosing spondylitis with severe forward displacement of the atlas; neurological complications were present in one case only and these disappeared after reduc-47 tion of the dislocation by skull traction. Brocher (1955) gave brief clinical descriptions of two men with ankylosing spondylitis and atlanto-axial subluxation; in one this was spontaneous but in the other it is possible that displacement may have followed tonsillectomy. Morrison (1955) referred to a 31-year-old soldier suffering from severe and rapidly-progressing ankylosing spondylitis who developed a tetraparesis which was at first attributed to protrusion of a cervical disk but was subsequently found to be due to atlanto-axial dislocation (Morrison, Baird, and Logue, 1957). Wilkinson and Bywaters (1958) mention a patient with ankylosing spondylitis who complained of neck pain in whom radiographs disclosed atlanto-axial subluxation, and Pratt (1959) described two patients with severe ankylosing spondylitis who developed spontaneous atlanto-axial dislocations, one of whom was treated by occipito-cervical fusion. Davis and Markley (1951) reported the clinical and autopsy findings in a 58-year-old female with severe nodular rheumatoid arthritis in whom the disease had resulted in severe destructive changes in the atlas, axis, and occiput with resulting dislocation of the atlas and compression of the medulla oblongata just below the pons by the odontoid process. The ganglion cells of the medulla showed pyknosis, eccentric nuclei, and vacuolization of the cytoplasm, but the brain and spinal cord were otherwise normal and there was no evidence of demyelination. Vignon and Patet (1955) described a 46-year-old woman who had developed an atlantoaxial displacement in association with rheumatoid arthritis of 8 years' duration. Storey (1958) reported the case of a 53-year-old woman with rheumatoid arthritis with a severe cord lesion who on 10 May 2018 by guest. Protected by copyright.

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1. Fifty-one cases of fracture of the odontoid have been analysed. Forty were reported by other surgeons; eleven were new cases first reported by us. 2. Fracture of the odontoid in young children is an epiphysial separation. It occurs up to the age of seven years. As in epiphysial separations elsewhere, it unites readily, and remodelling occurs when reduction has been incomplete, so that normal anatomy is restored. 3. In adults forward displacement is twice as common as backward displacement. 4. Immediate paralysis is commoner if backward displacement occurs, but late neurological disorders are seen only after fractures with forward displacement. 5. Failure of bony healing is not dangerous if treatment has resulted in firm fibrous union, for there is neither excessive abnormal mobility nor progressive subluxation, either of which could injure the spinal cord or medulla. Neurological disorders developing after the fracture are the result of mobility from inadequate early treatment. It is the results of inadequate early treatment which have given this fracture a sinister reputation. 6. The fracture should be reduced by skeletal traction through a skull caliper. The reduction should be maintained for six weeks by continuous traction, and this should be followed by a period of six weeks in a plaster. 7. The increasing definition of the fracture-line seen in the radiographs of some patients indicates non-union.

The behaviour of single units in the medial geniculate nucleus of the unanaesthetized unrestrained cat has much in common with that of units in auditory cortex, in terms of response categories and their relative proportions. The antero-posterior axis of the nucleus exhibits a very weak tonotopicity similar to that found in cortex. As in cortex, units responding to frequency change are often completely direction specific. On the other hand a high proportion of tone responsive units do so with inhibition. An apparently unique feature is the existence of ‘W-units’ which exhibit wide-band inhibitory response curves with a central region of excitation.

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