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neurological deterioration. The difficult decisionsconcern children with suspected cord tethering butapparently non-progressive neurological deficit or noneurological involvement at all. The proceedings ofthe first Stonwin conference,8 held in the USA,discuss these difficult decisions; of the sixteencontributors there are ten neurosurgeons, three

neuroradiologists, a paediatric pathologist, a plasticsurgeon, and a urologist. Although ultrasonographyof the spine is capable of detecting tethering, thefeeling is that, at least at present, it is insufficientlyreliable for a non-invasive screening test. Magneticresonance imaging is very promising, but, until moreexperience has accrued, CT-assisted myelographywith water-soluble contrast media is the definitive

diagnostic investigation. All the contributors felt that anewborn baby with a lumbosacral lipoma andtethered cord but no neurological abnormalitiesshould have surgery in the newborn period. Operationis no easier or safer if delayed until the infant is older,and there is a constant risk of insidious development ofa neurogenic bladder which would then be unlikely toimprove with surgery. Most believed that surgery wasalso indicated for an adolescent with a fixed

neurological deficit that involved bladder and bowel,with or without lower limb weakness; surgery wouldnot improve bladder or bowel function but wouldprevent progressive motor dysfunction in the legs. Ofparticular interest was the expert opinion that surgerywas indicated for symptomless adolescents or adultswith tethering. Although the tethered neurologicaltissues had survived the "tolerance test" of axial

growth, this group of patients are believed to be atcontinued risk of insidious progressive bowel andbladder dysfunction. In addition, sporting activitiesand minor trauma might jeopardise the vulnerablespinal cord, making sudden paraplegia a rare butdefinite hazard in patients who do not undergosurgery. Operative morbidity is very uncommon inexperienced hands, but there is a small risk ofincreased bowel and bladder dysfunction or legweakness. There are few definite contraindications to

surgery in patients with cord tethering. Indeed, theonly example given is that of the patient withlongstanding complete paraplegia and no bladder orbowel function.As for surgical technique, the conference view was

that monitoring of anal sphincter pressure or sensoryevoked potentials during surgery was helpful in

dissecting and preserving sacral nerves and in

identifying the filum terminale. The risk of

postoperative retethering can be reduced by ensuringthat untethered neurological elements remain bathedin spinal fluid, if necessary by use of a silastic duralsubstitute to effect a "roomy" dural closure. Finally, itwas agreed that an operation on a newborn baby with atethered cord was potentially hazardous and should becarried out only by an experienced paediatricneurosurgeon.8. Holtzman RNN, Stein BM, eds. The tethered spinal cord. New York: Thieme-

Stratton, 1985.

Depression and Cushing’sSyndrome

SINCE Harvey Cushing made his earliestobservations on the group of patients that bear hisname eponymously,1.2 it has become strikingly clearthat psychiatric disturbances are a common feature ofthe condition.3.4 The commonest abnormality ismental depression; it can range in severity from mildto catastrophically severe and tends to remit onceadrenal function returns to nonnal.5,6 Why individualpatients vary so widely in the manifestation of

psychiatric symptoms is unclear, but the pre-morbidpersonality is important since it appears to predict notonly the overall susceptibility but also the type ofdisorder. Early adverse life events or a family historyof depression or suicide may be common in patientswith Cushing’s syndrome, and it has even been

suggested that the syndrome represents a psycho-somatic disorder.8 Despite speculation about the

aetiological role of corticotropin (ACTH) and relatedpeptides, there is abundant evidence from the use ofsynthetic corticosteroids and from patients with

hyperfunctioning adrenal tumours that gluco-corticoids, in particular cortisol, can precipitate themental dysfunction.As methods for functional investigation of the

hypothalamic-pituitary-adrenal axis became morerefined and more widely accessible, it was discoveredthat patients with depressive illness may have many ofthe biochemical features of Cushing’s syndrome, fromraised urinary steroid excretion9 to loss of the normalcircadian rhythm of plasma cortisol.10 Much attentionhas centred on impaired suppression of cortico-steroids by dexamethasone;lo it has even been

suggested that this response might aid diagnosis."There is disagreement about the normality of thecortisol response to insulin-induced hypoglycaemia inpatients with depression, in part due to the differentcriteria used by various workers. When the standardused is that the blood sugar should fall below 22

mmol/1 (40 mg/dl), depressed patients usually behavelike normal controls, whereas patients with Cushing’s

1. Cushing H. Psychiatric disturbances associated with disorders of the ductless glands.Am J Insanity 1913; 69: 965-90.

2. Cushing H. The basophil adenomas of the pituitary body and their clinicalmanifestations (pituitary basophilism). Bull Johns Hopkins Hosp 1932; 50: 137-85.

3. Spillane JD. Nervous and mental disorders in Cushing’s syndrome. Brain 1951; 74:72-94.

4. Trethowan WH, Cobb S. Neuropsychiatric aspects of Cushing’s syndrome. ArchNeurol Psychiatry 1952; 67: 283-309.

5. Jeffcoate WJ, Silverstone JT, Edwards CRW, Besser GM. Psychiatric manifestationsof Cushing’s syndrome: Response to lowering of plasma cortisol. Quart J Med1979; 48: 465-72.

6. Kelly WF, Checkley SA, Bender DA, Mashiter K. Cushing’s syndrome anddepression—a prospective study of 26 patients. Br J Psychiatry 1983; 142: 16-19.

7. Cohen SI. Cushing’s syndrome: A psychiatric study of 29 patients. Br J Psychiatry1980; 136: 120-24.

8. Gifford S, Gunderson JG. Cushing’s disease as a psychosomatic disorder: A report often cases. Medicine (Baltimore) 1970; 49: 397-409.

9. Carroll BJ, Curtis GC, Davies BM, Mendels J, Sugarman AA. Urinary free cortisolexcretion in depression. Psychol Med 1976; 6: 43-50.

10. Butler PWP, Besser GM. Pituitary-adrenal function in severe depressive illness.Lancet 1968; i: 1234-36.

11. Carroll BJ, Feinberg M, Greden JF, et al. A specific laboratory test for the diagnosis ofmelancholia: Standardization, validation and clinical utility. Arch Gen Psychiatry1981; 38: 15-22.

551

syndrome do not increase their plasma cortisolconcentration adequately. Workers who use less

stringent criteria-eg, a fall in blood sugar below 50%of the basal level or to less than 50 mg/dl--sometimesreport that depressed patients do not increase theirplasma cortisol levels during insulin tolerance

testing.12,13The differential diagnosis of Cushing’s syndrome

and depression can therefore be difficult, at least onbiochemical grounds. It is perhaps surprising thatdepressed patients with such sustained hyper-cortisolism do not resemble those with Cushing’ssyndrome. The plethoric, overweight, hirsute,hypertensive diabetic may pose real difficulties,

, however, since obesity in its own right may conferbiochemical features reminiscent of Cushing’ssyndrome; the diagnosis then rests on a constellationof findings and the clinician must seek such valuablepointers such as features of enhanced proteinbreakdown-proximal muscle weakness and

wastingl4, skin atrophy, and osteoporosis.A new area of the central control of ACTH

secretion has opened up with the chemicalcharacterisation of the 41-residue peptide whichstimulates corticotropin release from the pituitary.is.Although the structures of the ovine and humanmolecules differ significantly, both are active in manand the ovine corticotropin-releasing factor (CRF)continues to be used in clinical investigations becauseof its slower disappearance from the plasma.16Challenging in their implications but of uncertainrelevance to human function and mood are

experiments showing behavioural changes afterintraventricular injection of CRF in rats. 17,18 There aresuggestions, however, that CRF levels are raised in thecerebrospinal fluid of patients with depression.19Against this background it comes as no surprise thatinvestigations have been conducted into the ACTHand cortisol responses to CRF in patients withdepression and Cushing’s disease. In depressedpatients, Gold and his colleagues at the NationalInstitutes of Health, Bethesda, have- shown that theACTH response to an injection of ovine CRF at2000 h is subnormal, although basal levels are slightly

12. Carroll BJ. Hypothalamic-pituitary function in depressive illness: Insensitivity tohypoglycaemia. Br Med J 1969; iii: 27-28.

13. Winokur A, Amsterdam J, Caroff S, Snyder PJ, Brunswick D. Variability of hormonalresponses to a series of neuroendocrine challenges in depressed patients. Am JPsychiatry 1982; 139: 39-44.

14. Ross EJ, Linch DC. Cushing’s syndrome-killing disease: Discriminatory value ofsigns and symptoms aiding early diagnosis. Lancet 1982; ii: 646-49.

15. Vale W, Spiess J, Rivier C, et al. Characterization of 41-residue ovine hypothalamicpeptide that stimulates secretion of corticotropin and &bgr;-endorphin. Science 1982;213: 1394-97.

16. Schûrmeyer TH, Avgerinos PC, Gold PW, et al. Human corticotropin-releasingfactor in man: Pharmacokinetic properties and dose-response of plasmaadrenocorticotropin and cortisol secretion. Clin Endocrinol Metab 1984; 59:1103-08.

17. Britton DR, Koob GR, Rivier J, Vale W. Intraventricular corticotropin-releasingfactor enhances behavioral effects of novelty. Life Sci 1982; 31: 363-67.

18. Sutton RE, Koob GF, LeMoul M, et al. Corticotropin releasing factor producesbehavioral activation in rats. Nature 1982; 293: 331-33.

19. Nemeroff CB, Widerlöv E, Bisette G, et al. Elevated concentrations of CSF

corticotropin-releasing factor-like immunoreactivity in depressed patients. Science1984; 226: 1342-44.

increased.2O By contrast, plasma cortisol is not onlyslightly increased under basal conditions but alsoshows an exaggerated rise after CRF. This is

interpreted as showing that the pituitary in depressionis essentially normal but is driven harder by thehypothalamus. The subsequent increase in plasmacortisol feeds back to diminish the ACTH response to

exogenous CRF. Patients with Cushing’s disease,however, appear to have a primary pituitaryabnormality in which the secretory capacity isincreased, leading to blunted negative feedback actionof cortisol but enhanced response to exogenous CRF.

Although the NIH study provides new insightsinto--1:he different mechanisms which can lead to

superficially similar states of pituitary ACTH-drivenhypercortisolism, it is hard to envisage that CRFstimulation will become a routine diagnosticprocedure; the ACTH radioimmunoassay is

technically difficult, and there is considerable overlapbetween the diagnostic categories. Moreover, most ofthe depressed patients had basal cortisol levels whichwould scarcely arouse the suspicion of Cushing’sdisease.

In the differential diagnosis of established

Cushing’s syndrome, CRF testing has its advocatesfor distinguishing pituitary-led Cushing’s diseasefrom ectopic ACTH secretion in particular, but mostendocrinologists tread very warily and believe that nosingle test is infallible. In this issue Dr Hermus and hiscolleagues (p 540) have stringently examined theCRF test in a prospective study of 26 patients andcompared it with the Liddle high-dose dexa-methasone test 21 Their findings confirm the value ofthe CRF test, with its occasional lapses, and arguestrongly for its inclusion as part of the standard

investigational protocol.

MENINGOCOCCAL INFECTIONS

INFECTIONS by Neisseria meningitidis have lately been ofconcern in Europe, in particular the severe disease caused bygroup B meningococci of type 15, subtype P1.16

(B:15:P1.16) and the interest this has aroused. A

symposium was held in Amsterdam last year to review theproblems associated with such infections, and the

proceedings have now been published.2 Apart from theseverity of disease associated with some outbreaks of

infection 3,4 the increased frequency in the 10-20 age groupShas brought the disease more into the public eye. The

20. Gold PW, Loriaux DL, Roy A, et al. Responses to corticotropin-releasing hormone inthe hypercortisolism of depression and Cushing’s disease. N Engl J Med 1986; 314:1329-35.

21. Liddle GW. Tests of pituitary-adrenal suppressibility in the diagnosis of Cushing’ssyndrome. J Clin Endocrinol Metab 1960; 20: 1539-60.

1. Editorial. Defences against meningococcal infection. Lancet 1985; ii: 929-30.2. International symposium on the emerging epidemic of meningococcal disease in NW

Europe. Antonie van Leeuwenhoek 1986; 52: 197-271.3. Holten E. Serotypes of Neisseria meningitidis isolated from patients in Norway during

the first six months of 1978. J Clin Microbiol 1979; 9: 186-88.4. Bøvre K, Frøholm LO, Goustad P, Holten E, Høiby EA. Some agent characteristics

and their co-existence related to occurrence and severity of systemic meningococcaldisease in Norway 1981-82. NIPH Ann 1983; 6: 75-84.

5. Abbott JD, Jones DM, Painter MJ, Young SEJ. The epidemiology of meningococcalinfections in England and Wales, 1912-1983. J Infect 1985; 11: 241-57.