Pseudopseudohypoparathyroidism and spinal cord compression

A 42 year old Greek male with pseudo-pseudohypoparathyroidism presented with difficulty in walking and with lower limb weakness. His physical signs included short stature, thick neck, short fourth metacarpals and metatarsals, and a spastic paraparesis. Serum calcium and phosphate and parathyroid concentrations were normal. Myelography demonstrated compression of the cervical and lumbar cord in association with local bony abnormalities.

Oral sumatriptan in acute migraine

The efficacy in acute migraine of oral sumatriptan was assessed in a double-blind, randomised, placebo-controlled, crossover study of 61 patients (mean age 39 [SD 10] years). 41 completed treatment of four attacks, two with sumatriptan 100 mg and two with placebo. The response rate (reduction in headache from moderate or severe to mild or absent at 2 h) was 51% (45/89) with sumatriptan and 10% (9/93) with placebo (p less than 0.01); rescue medication was needed at 2 h in 41% and 88%, respectively. Of 28 patients headache-free at 24 h, 11 (39%) had recurrent headache within 24 h. There were no substantial side-effects. Thus, sumatriptan is an effective well-tolerated treatment for acute migraine attacks.

Neural processing of craniovascular pain: a synthesis of the central structures involved in migraine

In order to determine the anatomical distribution of cells concerned with relaying craniovascular nociception, local cerebral glucose utilization was determined by the 2-deoxyglucose method in tissue autoradiographs of the alpha-chloralose anesthetized cat. The superior sagittal sinus was carefully lifted from the brain by sectioning the dura laterally and the falx inferiorly and suspending the sinus across two platinum hook electrodes for stimulation. The sinus was stimulated electrically and its effect on caudal brainstem, upper cervical spinal cord and diencephalic metabolic activity determined. Stimulation of the sinus caused increased metabolic activity in the trigeminal nucleus caudalis, in the cervical dorsal horn and in a discrete area in the dorsolateral spinal cord at the second cervical segment. Metabolic activity was also increased in the ventrobasal thalamus, specifically in the ventroposteromedial (188%) nuclear group, in the medial nucleus of the posterior complex (70%) and the intralaminar complex (49%). There was no change in the surrounding thalamus, lateral geniculate nucleus or overlying cerebral cortex. These increases in 2-deoxyglucose utilisation were blocked by bilateral trigeminal ganglion ablation. The dorsolateral area activated in the spinal cord corresponds to a hitherto unrecognised group of cells in or near the lateral cervical nucleus that may form an important relay for craniovascular nociception. Further electrophysiological studies with glass coated tungsten microelectrodes have characterised the cells in these regions of the thalamus to be responsible for relaying nociceptive information. An understanding of the connections and properties of the neurons that subserve craniovascular pain is an essential prerequisite to understanding the complex pathophysiology of migraine.

Stimulation of the superior sagittal sinus increases metabolic activity and blood flow in certain regions of the brainstem and upper cervical spinal cord of the cat

To investigate the anatomical distribution of cells concerned with relaying craniovascular nociception, local cerebral blood flow was examined in the cat using the tracer [14C]-iodoantipyrine and local cerebral glucose utilization determined by the 2-deoxyglucose method in tissue autoradiographs. The superior sagittal sinus was stimulated electrically and its effect on caudal brainstem and upper cervical spinal cord blood flow and metabolism evaluated. This caused increased metabolic activity and blood flow in the trigeminal nucleus caudalis, in the cervical dorsal horn and in a discrete area in the dorsolateral spinal cord at the second cervical segment. Responses in these 3 areas were blocked by ablation of the trigeminal ganglia. The dorsolateral area activated in the spinal cord corresponds to a group of cells in or near the lateral cervical nucleus that may form an important relay for craniovascular nociception and thus be of relevance to the mechanism of headache.

Localization of 3H-dihydroergotamine-binding sites in the cat central nervous system: relevance to migraine

Dihydroergotamine (DHE) is the treatment of choice in aborting the acute attack of migraine. Although its efficacy has been known for 40 years, its mechanism of action is still disputed. Data regarding the site of action of dihydroergotamine may provide an insight into its mechanism of action and thus identify a locus of potentially abnormal pathophysiology in migraine. By using in vitro and ex vivo autoradiographic techniques, the localization of specific binding sites for 3H-dihydroergotamine in the cat brain has been examined. Binding was seen in the dorsal horn of the cervical spinal cord, in the medulla, associated with the nucleus of the tractus solitarius, area postrema, and descending spinal trigeminal nucleus, and in the mesencephalon and the cerebral cortex. The highest density of binding sites was found in the dorsal and medial raphe nuclei of the midbrain. Furthermore, these same brain regions were also labeled after intravenous administration of 3H-dihydroergotamine. It is important that the brain areas specifically labeled are key nuclei involved in cranial pain transmission, suggesting that dihydroergotamine may act at these central sites in migraine.

Characteristics of facial nerve-elicited cerebral vasodilatation determined using laser Doppler flowmetry

Cerebral cortical perfusion was monitored continuously with laser Doppler flowmetry and quantitative measurements of cerebral blood flow performed with the freely diffusible tracer 4-iodo[N-methyl-14C]antipyrine in the alpha-chloralose-anesthetized cat. The facial nerve was isolated from the brain stem via a posterior fossa craniotomy and electrically stimulated at frequencies of 1, 2, 5, 10, and 20 s-1. A stimulus-locked frequency-dependent increase in cerebral perfusion was seen in the parietal cortex; the mean maximum increase was 91 +/- 22% at 20 s-1. This compared with an absolute flow of 116 +/- 3 ml.100 g-1.min-1 at the same site. In addition, the response was associated with a marked increase in cerebral venous O2 content indicating that it is a primary neurogenic dilator response. This response could be blocked by hexamethonium but not by atropine and was thus mediated by an autonomic ganglion but not by the classical muscarinic postsynaptic receptor. Sectioning of the facial nerve did not alter cerebrovascular reactivity to hypercapnia. These data confirm the vasodilator effect of activation of the facial nerve and document its mediation through an intermediate parasympathetic ganglion. Consistent with previous data, the facial nerve does not appear to play a role in hypercapnic cerebral vasodilatation. Furthermore, this study highlights the usefulness of laser Doppler flowmetry in the cerebral circulation and in particular in the setting where repeated measures are required, such as in pharmacological studies.

Vasoactive peptide release in the extracerebral circulation of humans during migraine headache

The innervation of the cranial vessels by the trigeminal nerve, the trigeminovascular system, has recently been the subject of study in view of its possible role in the mediation of some aspects of migraine. Since stimulation of the trigeminal ganglion in humans leads to facial pain and flushing and associated release of powerful neuropeptide vasodilator substances, their local release into the extracerebral circulation of humans was determined in patients who had either common or classic migraine. Venous blood was sampled from both the external jugular and cubital fossa ipsilateral to the side of headache. Plasma levels of neuropeptide Y, vasoactive intestinal polypeptide, substance P, and calcitonin gene-related peptide were determined using sensitive radioimmunoassays for each peptide, and values for the cubital fossa and external jugular and a control population were compared. A substantial elevation of the calcitonin gene-related peptide level in the external jugular but not the cubital fossa blood was seen in both classic and common migraine. The increase seen in classic migraine was greater than that seen with common migraine. The other peptides measured were unaltered. This finding may have importance in the pathophysiology of migraine.

Stimulation of the superior sagittal sinus in the cat causes release of vasoactive peptides

External jugular vein blood was sampled in the anesthetized cat during electrical stimulation of the superior sagittal sinus (SSS), and the levels of calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), substance P (SP) and neuropeptide Y (NPY) were measured with sensitive radioimmunoassays. CGRP levels rose by 85% and VIP levels by 300% while there was no change in SP or NPY levels in the same samples. These data provide the first evidence that activation of the trigeminovascular system, by selective stimulation of nociceptive craniovascular afferents, causes releases of vasodilator peptides and further implicates this system in the pathophysiology of migraine.

High-frequency stimulation of the facial nerve results in local cortical release of vasoactive intestinal polypeptide in the anesthetised cat

Local cortical release of vasoactive intestinal polypeptide (VIP) was measured using a sensitive radioimmunoassay following direct electrical stimulation of the facial nerve in the anaesthetised cat. During activation of the facial nerve dilator pathway VIP was released at the cortex and collected into a physiological superfusate, its concentration increasing from 4.2 +/- 1.2 to 15.5 +/- 2.4 pmol/l. Administration of the nicotinic ganglion blocking agent hexamethonium (10 mg/kg i.v.) eliminated this response demonstrating that the release is mediated via an autonomic ganglion. Given previous experiments that have demonstrated that stimulation of the facial nerve leads to a neurogenically mediated dilatation of the cerebral vasculature, these data further implicate VIP as the transmitter in this pathway.

[Physiopathology of migraine]

In those subjects genetically susceptible to migraine, biological rhythms or excessive afferent stimulation trigger an episodic neurovascular reaction with focal neurological symptoms, headache and nausea as its most common manifestations. Mood changes and a craving for sweet foods point to a preliminary hypothalamic disturbance. The referral of ice-cream headache and ice-pick pains to the habitual site of migraine headache (even in the intervals between attacks) indicate defective control of trigeminal pathways. Laboratory experiments have demonstrated that projections from the brainstem, releasing monoamines and peptides as transmitter agents, can mimic the vascular changes of migraine. Serotonin released from platelets may sensitize vessels to respond to distension by generating pain-producing afferent discharges. Central depletion of monoamines can accentuate the perception of pain by reducing the efficacy of the endogenous pain control system. The intravenous injection of serotonin relieves migraine headache but produces side-effects. A new drug, sumatriptan, acting on a subtype of serotonin receptors, the 5HT1-like receptor, is undergoing clinical trial for the relief of acute attacks of migraine. Antagonist of the 5HT2 receptor are beneficial in interval therapy for the prevention of migraine. Increased knowledge of physiological mechanisms and neurotransmitters that can mediate the various components of the migraine attack opens the way for improvements in pharmacotherapy.

Sphenopalatine ganglion stimulation increases regional cerebral blood flow independent of glucose utilization in the cat

Regional cerebral blood flow was determined using the tracer [14C]iodoantipyrine and regional brain dissection, and regional cerebral glucose utilization determined using the 2-deoxyglucose method, in the alpha-chloralose-anesthetized cat to evaluate the effect of electrical stimulation of the sphenopalatine (pterygopalatine) ganglion. Unilateral stimulation for either a short period (7-10 min) or a longer period (45 min) resulted in increases in blood flow in the ipsilateral cerebral cortex of up to 45% (parietal cortex) with, in addition, increased flow in the white matter of the corpus callosum (42%). The flow changes for both brief and prolonged stimulation were not significantly different. Flow was not altered in either the brainstem or basal ganglia (caudate nucleus). In contrast to these changes in cerebral blood flow no changes in cerebral glucose utilization were seen in any of the brain areas studied and in particular there were no changes in the areas in which blood flow increased. These data provide clear evidence that the innervation of the cerebral vasculature from the main parasympathetic ganglion can alter cerebral blood flow independent of cerebral metabolism.

Electrical stimulation of the fastigial nucleus increases total cerebral blood flow in the monkey

Internal and external carotid blood flows were monitored continuously in the barbiturate-anesthetized monkey with appropriately-sized electromagnetic flow probes. Electrical stimulation of the fastigial nucleus increased blood flow in both the internal and external carotid circulations in a frequency-dependent manner. This response was entirely intracerebral and independent of infra-bulbar mechanisms since it was present following high cervical spinal cord section. These data re-affirm the presence of the fastigial nucleus cerebral vasodilator response and add the observations that the response is present in the primate and markedly frequency-dependent.

Clinicopathological correlation in a case of painful ophthalmoplegia: Tolosa-Hunt syndrome

A case of painful ophthalmoplegia due to idiopathic granulomatous involvement of the superior orbital fissure (Tolosa-Hunt syndrome) is described. The clinical features of recurrent pain, ocular motor nerve palsies and proptosis correlated well with the eventual demonstration of an enhancing mass in the region of the cavernous sinus. Removal of the lesion led to a resolution of the clinical picture and demonstration of a non-caseating granuloma with no other detectable cause. The original observation of Tolosa was thus re-affirmed.

Effect of stimulation of facial nerve on regional cerebral blood flow and glucose utilization in cats

Regional cerebral blood flow was determined using the tracer [14C]iodoantipyrine and regional brain dissection, and regional cerebral glucose utilization was determined using the 2-deoxyglucose method in the alpha-chloralose-anesthetized cat to evaluate the effect of electrical stimulation of the facial nerve. The nerve was sectioned intracranially to isolate it from the brain stem and the distal portion stimulated before entry into the internal auditory meatus. Stimulation led to a global increase in cortical (frontal, parietal, temporal, occipital, and cingulate cortex) and white matter blood flow. This effect was predominantly ipsilateral to the side stimulated, although significant effects were also noted on the contralateral side. The latter were confined to the more anterior cortical structures. In contrast, there were no significant changes in regional metabolic activity as assessed by the rate of glucose utilization. This study provides direct evidence for a neurogenic vasodilator effect of activation of the facial-greater superficial petrosal pathway that is independent of regional brain metabolic activity.

Massive benign thymoma presenting as ocular myasthenia

A case of ocular myasthenia was found to be associated with a massive benign thymoma and responded to its removal. This is an exception to the generalisation that larger tumours of the thymus gland are more likely to be malignant and that thymectomy is not the treatment of choice for ocular myasthenia.

Low frequency stimulation of the locus coeruleus reduces regional cerebral blood flow in the spinalized cat

Regional cerebral blood flow (RCBF) was studied during low frequency (15/s) and high frequency (50/s) electrical stimulation of the locus coeruleus (LC) in the alpha-chloralose-anesthetized cat using the freely diffusible tracer [14C]iodoantipyrine and regional brain dissection. The responses were determined in animals spinalized at the C1/C2 level to eliminate systemic effects of pontine stimulation such as alterations in blood pressure and heart rate. The spinalization, itself, did not alter resting RCBF or reactivity to hypercapnia. Low frequency stimulation reduced regional cerebral blood flow in the cortex, basal ganglia and white matter of the corpus callosum. The reductions in RCBF were maximal (35%) in the occipital cortex whereas no changes were seen in the colliculi. No changes were seen in any brain areas with high frequency stimulation. The relevance of this brainstem effect on cerebral blood flow to pathological states such as stroke and migraine is discussed.

Comparative effects of stimulation of the trigeminal ganglion and the superior sagittal sinus on cerebral blood flow and evoked potentials in the cat

The superior sagittal sinus (SSS) and the trigeminal ganglion (Vg) of anesthetized cats were stimulated electrically and field potentials in the upper cervical spinal cord and regional cerebral blood flow were recorded. Stimulation of the entire ganglion produced smaller field potential changes in two regions (medioventral area (MVA); dorsolateral area (DLA] of the upper spinal cord than did stimulation of the sagittal sinus (Vg/SSS response ratio = 17% for the MVA and 48% for the DLA). Stimulation of the trigeminal ganglion increased blood flow in only the frontal and parietal cortices (+93% and +33%), whereas stimulation of the sinus produced both larger changes in these areas (+137% and +139%) and also produced changes in regional cerebral blood flow in the thalamus (+122%).

Release of vasoactive peptides in the extracerebral circulation of humans and the cat during activation of the trigeminovascular system

The trigeminal ganglion was activated, in humans by thermocoagulation as part of the treatment of trigeminal neuralgia and in cats by electrical stimulation, and blood samples were taken from the external jugular vein for estimates of plasma levels of substance P and calcitonin gene-related peptide (CGRP). In those patients who were noted at the time of coagulation to have flushed there were marked elevations of the local (cranial) levels of both peptides. However, in the nonflushing patients no changes in the peptide levels were observed. Parallel experiments in the cat revealed that the levels of substance P-like and CGRP-like immunoreactivity were increased during electrical stimulation of the trigeminal ganglion. The observation of elevation of substance P-like and CGRP-like immunoreactivity after activation of the nociceptive afferent system of the head provides new insights into a putative role of peptides in the pathophysiology of migraine and cluster headache, and suggests new areas of possible therapeutic intervention.

Effect of stimulation of trigeminal ganglion on regional cerebral blood flow in cats

Regional cerebral blood flow was studied in the cat, with and without trigeminal ganglion stimulation, by the intravenous injection of the tracer [14C]iodoantipyrine and subsequent regional brain dissection. Electrical activation of the trigeminal ganglion led to a selective increase in regional blood flow in the frontal and parietal cortex that was bilateral without change in the posterior cortex, deep cerebral nuclei, white matter, or brain stem. Unilateral intracranial section of the facial nerve blocked the response in the ipsilateral frontal and parietal cortex, whereas bilateral facial nerve section blocked the contralateral frontal cortical response. The contralateral parietal cortical increase in blood flow was not affected by facial nerve section and may thus represent the result of metabolic activation of sensory cortex.