latencies in the normal in their patients. They did not furnish the actual values and did not compare these latencies with those in the normal limbs. It is possible that their latencies in hemiplegic limbs may not have been "normal" compared with the values in the normal limbs of their patients. In fact, we reported in our study that in three patients (No. 2, 6, and 10), the brachial plexus latencies in the hemiplegic arms were prolonged as compared with those in the unaffected arms, although both the values were within the accepted normal range. Whether the abnormal latencies in our patients could be compatible with decreased skin temperature in the hemiplegic side is a pertinent question. However, in our study we noted that skin temperature was reduced in the hémiplégie side in 22 of 35 patients, and the reduction was greater in the legs than in the arms. We noted a significant correlation of reduced skin temperature with slow¬ ing of the peroneal nerve conduction velocity, but not with distal conduc¬ tion velocities in the upper limb nerves. We therefore think it is unlikely that the abnormal brachial plexus latencies in our study were related to the factor of limb tempera¬
Finally, regarding the question of appropriateness of an intramuscular thermocouple electrode, we like to state that such
electrode does not
necessarily reflect the true tempera¬ ture in all regions of the nerve.
Lambert1 stated that some parts of the nerve are cooled or warmed to a greater degree than the deep muscle in which the temperature is mea¬ sured. S. Chokroverty, MB, BS, MRCP Neurol Service and Research Lab VA Hosp Hines, IL 60141 1. Lambert EH: Diagnostic value of electrical stimulation of motor nerves. Electroencephalogr Clin Neurophysiol 22(suppl):9-16, 1962.
Spinal Deformities: A Neurosurgeon's Viewpoint To the Editor.\p=m-\TheCNS is nourished by CSF, which Cushing referred to as the "third circulation."1 It is the only organ with such a circulation, aside from the eye and the internal ear, which actually are part of the CNS. The closure of the neural groove to form a tube is completed on day 26, which is two weeks prior to the devel-
opment of the choroid plexuses. The
first fluid that progressively distends the neural tube is secreted by the cells lining its lumen. This primitive CSF contains a quantity of protein that increases in concentration during these intervening two weeks during which time the somites develop. The resulting increase in colloidal osmotic tension of this primitive CSF causes the neural tube to expand progressively during the presomite and somite stages. If this distention becomes pathologic in degree, which is not surprising, overexpansion of the primitive cord will spread and distort the precartilaginous sclerotomes as they develop on each side of the neural tube. Such overexpansion also may split the notochord, which develops as a diverticulum of the primitive gut in contact with the footplate of the spinal cord, to constitute the precursor of the intervertebral disks. An abnormal degree of distention of the neural tube may become compensated just as happens with the normal degree. Such compensation is an expression of the law of Laplace.2 If the overdistention becomes com¬ pensated sufficiently early, the new¬ born will appear completely normal but perhaps with somewhat widened fontanelles. Nevertheless, hidden damage to vertebral primorida, which in some instances produce hemivertebrae, subsequently may eventuate in scoliosis, because weight bearing dur¬ ing infancy and adolescence has converted the horizontal spinal beam into a weight-bearing vertical column. Kyphoscoliosis may be obvious at birth if the overdistention of the neural tube had been sufficient to cause its rupture with resulting myelocele. When I was a medical student, embryology was taught in the fresh¬ man year, and as soon as the examina¬ tion was passed, the student dismissed it from his mind only to relearn it later in his search for the cause of the dysraphic states.3 At the present time, embryology and teratology are cov¬ ered very superficially if at all, because the tremendous expansion of medical knowledge has crowded them out of the curriculum. The first Tera¬ tology Society was founded in 1960, and the majority of its present 600 members hold PhD degrees in anato¬ my. I joined this organization in 1961, but my continuing efforts have con¬ vinced very few of its members that anencephaly and myelocele are not the result of failure of the neural tube to close but of its rupture from overdis¬ tention following it closure. Only the
neurosurgeon is able to study this unique third circulation in the living patient, and in both its physiologic and pathologic states. Physiology can¬ not be observed through the micro¬ scope. W. J. Gardner, MD Cleveland Clinic Foundation Cleveland, OH 44106
1. Gardner WJ: The brain's third circulation. Arch Neurol 34:200, 1977. 2. Gardner WJ: Hydrodynamic factors in Dandy-Walker and Arnold-Chiari malformations. Child Brain 3:200-212, 1977. 3. Gardner WJ: Why anomalies of the CSF circulation are so common? Arch Neurol 34:517, 1977.
Huntington's Chorea Bromocriptine
To the Editor.\p=m-\Weread with interest the letter from Frattola et al (35:60, 1978) about the mechanisms of action of bromocriptine in Huntington's chorea. According to the authors, bromocriptine should be considered as a partial dopaminergic agonist, with a "biphasic effect" that depends on the
Similar effects have been observed
by us after the administration of bromocriptine to 11 patients affected by Huntington's chorea1: involuntary movements showed a good improvement when the daily dosage of bromocriptine was low (< 40 mg/day), whereas a slight worsening was seen after the administration of higher dosages (40 to 60 mg/day). Moreover, CSF HVA levels substantially increased after the low-dosage treatment with bromocriptine, and substantially decreased when a high dosage was used. These data, namely, the increase in CSF HVA levels associated with the clinical improvement of choreic movements, suggest that dopamine-sensitive receptors in the neostriatum are blocked, from a low daily dose of
like effect. On the contrary, the decrease in CSF HVA and the clinical worsening observed after treatment with higher doses of the drug make it conceivable that, under these condi¬
tions, dopamine-sensitive receptors are hyperstimulated.
Claudio Albano, MD Leonardo Cocito, MD Neurology Clinic University of Genoa Via de Toni, 5 16132
1. Loeb C, Roccatagliata G, Albano C, et al: Effects of bromocriptine in Huntington's chorea. Neurology, to be published.
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