ABSTRACTS

apy. If replicated by other investigators, this modality may prove useful in superficial lesions because of the energy of applied photons. Another therapeutic appli- cation would be its use in patients with multiple le- sions or lesions overlying vital structures. Further studies with human squamous carcinoma cell lines, in vitro and in vivo, should be conducted before this technique is investigated in humans. Nevertheless, this is an irradiation technique that warrants atten- tion

Molecular Biology of Brain Tumors. JD McDonald, GJ Dohrmann. Neurosurgery 1988; 23:537-544

This is a review article on the molecular biology of brain tumors. Although the focus of discussion is cen- tered on brain tumors, it is a nice review of current techniques, problems, and advances in molecular bi- ology as applied to the general problem of neoplasia. Specific examples of recent work on tumors using ba- sic techniques-Southern and Northern blots, re- stricted enzyme digestion of DNA, molecular cloning of genes, and mapping of chromosomal lesions-are reviewed. In addition, oncogene control mechanisms in tumor cells are discussed. The more recent concept of recessive oncogenes is considered in relation to studies using patients with bilateral acoustic neurino- mas and retinoblastoma. This article is a valuable summary of the most recent types of laboratory inves- tigations that are also being applied to head and neck tumors. Future clinical implications of the findings are also discussed. For example, a standard part of the current staging of some solid tumors (eg, neuroblas- toma) includes following the levels of oncogene copy number. Similarly, work on the amplification of growth factor receptors in tumor cells may guide the development of future treatment strategies. The study of recessive oncogenes in acoustic neurinoma is of more immediate clinical importance. These findings are consistent with the possibility that a lesion on chromosome 22 may represent the primary event in the pathogenesis of some acoustic neurinomas. The localization of the gene or genes involved should lead to advances in prenatal diagnosis. In short, this paper is a succinct summary of the role of molecular biology and its application in understanding the process of neoplasia, as well as the clinical issues involved.

Magnetic Resonance Imaging of the Head and Neck Region. HG Jacobson. JAMA 1988; vol 260.

Magnetic resonance imaging (MRI) is increasingly being used in the head and neck region, and in some cases replaces computed tomography (CT) imaging. This article reviews the major strengths and weak- nesses of MRI of the extracranial head and neck struc- tures. MRI and CT should be complementary, rather than exclusive, modalities. The major strengths of MRI include excellent cell-tissue contrast, non- invasiveness, and lack of ionizing radiation. The im- proved contrast resolution of MRI over CT has led to

greater sensitivity in studying individual pathways of cranial nerves in the posterior fossa. MRI is also very useful in vascular lesions because of its slow sensitive gradient--echo pulse sequences. The potential use of rapid scanning techniques in conjunction with para- magnetic contrast agents may produce imaging similar in quality and content to dynamic, contrast-enhanced CT scans. MRI has fundamental limitations for show- ing bone detail; in this regard, CT is still the favored imaging modality. However, MRI can be very sensitive in assessing the infiltration of lesions into the bone marrow. MRIs are excellent in viewing pathology of the skull base, salivary glands, paranasal sinuses, tem- poral bone, and orbit. It is noted that MRIs are expen- sive, and the additional information gained, when compared with other techniques, may not always jus- tify the cost. Although some current papers enthusi- astically suggest that MRI should be the radiographic examination of choice, such advocacy should be seen in the context of the critical information presented in this paper. Continued attention to clinical correlation is necessary in the next few years to see if this tech- nique is indeed as excellent as it initially appears to be.

Role of Ionizing Irradiation for 393 Keloids. TL Borok, M Bray, I Sinclair, et al. Int J Radiat Oncol Biol Phys 1988; 15:865-870

This paper documents the 58-year experience of one institution in the treatment of 393 keloids scattered over different sites. It is a retrospective chart review examining recurrence rates, cosmetic results, and ra- diation-induced neoplasia. Indications for offering ra- diation included keloid at the original treatment site (88%), documented multiple significant keloid forma- tion (I%), and a strong family history of keloid forma- tion (l%]. The most commonly given dose was 900 to 1,000 cGy. The most common site of recurrence fol- lowing excision was in the ear lobes of young females with pierced ears. Recurrence rate after radiation was low (2.4%) and the cosmetic result was considered excellent in approximately 92%. Significant compli- cations were limited to persistent pigment distur- bance in only one patient. In this series, no cases of neoplasia were seen, although it is unclear whether there was a 100% follow-up for all the cases studied. This is an interesting study that would support the use of radiation therapy when keloid formation is a con- cern. However, a strict comparison between this tech- nique and steroid injection has not been made. In ad- dition, one should view with great caution the use of low-dose irradiation in young people in the treatment of a primarily cosmetic problem.

Hypoxia and Hypercapnia in Infants with Mild Laryngomalacia. PB McCray, DM Crockett, et al. Am J Dis Child 1988; 142:896-899

Volume 10 Laryngomalacia accounts for more than 75% of

cases of congenital stridor and is the most common Number 4

July 1989

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