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Control of cerebral blood flow.

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LETTERS
Control of Cerebral
Blood Flow
Sally J. Boyson, MD
The review of control of cerebrovascular blood flow by Lou
and colleagues (Ann Neurol 1987;22:289-297) cited work
by Sharkey and McCulloch demonstrating an increase in the
ratio of flow to glucose utilization produced by a DZ- but not
a D1-selective agonist. The logical conclusion, that Dz receptors may regulate blood flow but that D1 receptors do not, is
not necessarily sound. The D1-selective agonist used, SKF38393, is a partial agonist 11). While at low doses this will
stimulate D1 receptors, at high doses a partial agonist will
actually inhibit the maximal response. Until the effects of a
full agonist selective for D1 receptors are examined, it would
be premature to conclude that D1 receptors do not also
regulate cerebral blood flow. The fact that we found a low
level of D1 receptors throughout the rat brain 123 suggests
that they might indeed be located on blood vessels.
University of Colorado Health Sciences Center
Denver, CO
Refwences
1. Leff SE, Hamblin MW, Creese I. Interactions of dopamine agonists with brain D1receptors labeled by 3H-antagonists.Evidence
for the presence of hlgh and low affinity agonist-binding states.
Mol Pharmacol 1985;27:171-183
2. Boyson SJ, McGonigle P, Molinoff PB. Quantitative autoradiographic localization of the D, and DZsubtypes of dopamine receptors in rat brain. J Neurosci 1986;6(11):3177-3188
It is important to realize that: (1) apart from the wellknown signs and symptoms of cervical myelopathy, nystagmus and weakness of facial muscles should also raise suspicion of atlantoaxial dislocation; (2) patients can become
symptomatic even in their mid-40s; and (3) important clinical
improvement after surgery is possible even in cases with
severe cervical myelopathy of prolonged duration.
Asymptomatic atlantoaxial dislocations are also recognized. In these cases the ratio of males to females is 1:1, and
odontoid malformations are found in 6%. In symptomatic
cases these figures are 1:2.3 to 1:4 and 60% respectively.
Therefore, special attention should be given to female patients and to those with odontoid malformations.
Institute of Neurology
University Hospital Nzjmgen
Nijmegen, The Netherlands
References
1. Chaudry V, Sturgeon C, Gates AJ, Myers G. Symptomatic atlantoaxial dislocation in Down’s syndrome. Ann Neurol 1987;21:
606-609
2. Pueschel SM, HerndonJH, Gelch MM, et al. Symptomatic atlantoaxial subluxation in persons with Down syndrome. J Pediatr
Orthop 1984;4:682-688
3. Braakhekke JP, Gabreels FJM, Renier WO, et al. Craniovertebral pathology in Down syndrome. Ciin Neurol Neurosurg
1985;87:173-179
4. Semine AA, Ertel AN, Goldberg MJ, Bull MJ. Cervical-spine
instability in children with Down syndrome (trisomy 21). J Bone
Joint Surg 1978;60A:649-652
5. Pueschel SM. Atlanto-axial subluxation in Down syndrome. Lancet 1983;1:980
Reply
Hans Lou, MD, PhD
Systemic Sclerosis:
Another Disease with
Autonomic Dysfunction
We accept the interpretation given by Sally J. Boyson.
John F . Kennedy Instituttet
Glostrup, Denmurk
R. F. Gledhill, MD,*? and P. H. M. C. Dessein, MDt
Symptomatic
Atlantoaxial Dislocation
in Down’s Syndrome
J. P. Braakhekke, MD
Symptomatic atlantoaxial dislocation occurs in Down’s syndrome, as pointed out by Chaudry and colleagues [l). Two
additional papers on this subject 12, 33 have appeared recently. The condition is not as rare as suggested by Chaudry
and associates. In epidemiological studies, symptomatic atlantoaxial dislocation is found in 1.2 to 2.5% of the patients
with Down’s syndrome [4,5]. Through 1985,8 patients with
orthopedic symptoms (limited neck mobility, neck pain, torticollis, head tilt) and 37 patients with cervical myelopathy
have been reported.
We have just completed a study of autonomic function in
patients with various connective tissue diseases and wish to
nominate systemic sclerosis as an addition to the list of disorders specified by McLeod and Tuck El} in their recent review.
Three patients with systemic sclerosis [2} were studied,
this being the total number of patients with this disease
under our care at the time. All were women, ranging in age
from 41 to 44 years. None had diabetes, renal failure, or
clinical signs of cardiovascular disease. Each was a nonsmoker
and denied any alcohol consumption. N o patient was receiving drug therapy in dosages known to affect cardiovascular or
peripheral (somatic) nerve function.
Autonomic function was evaluated using the 5 cardiovascular tests described by Ewing and Clarke [3]. Compared to
results in sex- and race-matched healthy volunteers (control
subjects) (median age 38 years), 2 of the 5 test results were
abnormal in Patient 1, 3 were abnormal in Patient 2, and 4
Copyright 0 1988 by the American Neurological Association 42 1
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