C7 radiculopathy: importance of scapular winging in clinical diagnosis.

Lesions of the seventh cervical (C7) root are common and cause a readily recognised neurological syndrome. Recognition of this pattern is essential in differentiating C7 root lesions from lesions of the brachial plexus or peripheral nerves. Serratus anterior weakness is not generally included in this syndrome. We report six verified cases of C7 radiculopathy in which weakness of the serratus anterior was present in addition to the usual findings. This was manifest as winging of the scapula, when pushing forward against a wall, either with the hands at shoulder level or, in some cases, only when the hands were lowered to waist level. This latter method of testing places the muscle at a mechanical disadvantage and reveals partial paralysis. Analysis of this clinical finding complements anatomical evidence suggesting that the powerful lower digitations of the muscle may be primarily supplied by the C7 root in some cases. Scapular winging, apparent either in the usual position or the modified position described here, should be recognised as consistent with a diagnosis of C7 radiculopathy. When present, this sign serves to differentiate C7 radiculopathy from lesions of the brachial plexus or radial nerve.

Major cerebral arterial and venous disease in osteopetrosis.

Two patients with osteopetrosis were studied in whom severe stenosis of one or both internal carotid arteries was demonstrated. One patient had autosomal dominant osteopetrosis and the other patient had the autosomal recessive form of the disease. In one patient, probable occlusion of one internal jugular vein and retrograde thrombosis of the contributing dural venous sinuses was present. Venous drainage of parts of the brain occurred through dilated emissary and scalp veins. It appears that major extracranial vessels may be impinged upon by dysplastic bone in osteopetrosis, although this is the first report of such an occurrence. A posterior fossa aneurysm was present in one case, and may have been related to abnormal intracranial hemodynamics.

Asymmetric effects of deletions and substitutions on high negative interference in coliphage lambda.

Experiments have been performed to help clarify the role of nonhomologies in phage lambda recombination. Three-factor crosses were carried out, and the frequencies of single and double recombinants in the two adjoining intervals were compared when the central marker was either a double point mutation (v1v3) or deletion (rex-cI deletion) or nonhomologous substitution (imm434). In all cases the lefthand marker was a bio substitution (Fec- phenotype, which does not permit plating on recA-), and the righthand marker was an amber mutation in gene O. Experiments were performed in all four possible arrangements of the central and rightward markers, while selecting for the Fec+ phenotype on the recA- host. As anticipated, high negative interference (HNI) was observed with point mutations, but when the central marker was a substitution nonhomology, HNI was reduced about tenfold. Surprisingly, when the central marker was a simple deletion, a dramatic asymmetry in results was observed, with HNI being exhibited only when the central deletion marker was acquired by the double recombinant. These results indicate that under normal conditions (red+, gam+, rec+) and with noninhibited DNA replication, recombination in coliphage lambda entails a highly asymmetric step that could be at the level of strand transfer or mismatch repair.