Indomethacin in the management of elevated intracranial pressure: a review

Indomethacin: The Interplay between Structural Relaxation, Viscous Flow and Crystal Growth

Non-isothermal differential scanning calorimetry (DSC) was used to study the influences of particle size (d_aver) and heating rate (q⁺) on the structural relaxation, crystal growth and decomposition kinetics of amorphous indomethacin. The structural relaxation and decomposition processes exhibited d_aver-independent kinetics, with the q⁺ dependences based on the apparent activation energies of 342 and 106 kJ·mol^-1, respectively. The DSC-measured crystal growth kinetics played a dominant role in the nucleation throughout the total macroscopic amorphous-to-crystalline transformation: the change from the zero-order to the autocatalytic mechanism with increasing q⁺, the significant alteration of kinetics, with the storage below the glass transition temperature, and the accelerated crystallization due to mechanically induced defects. Whereas slow q⁺ led to the formation of the thermodynamically stable γ polymorph, fast q⁺ produced a significant amount of the metastable α polymorph. Mutual correlations between the macroscopic and microscopic crystal growth processes, and between the viscous flow and structural relaxation motions, were discussed based on the values of the corresponding activation energies. Notably, this approach helped us to distinguish between particular crystal growth modes in the case of the powdered indomethacin materials. Ediger's decoupling parameter was used to quantify the relationship between the viscosity and crystal growth. The link between the cooperativity of structural domains, parameters of the Tool-Narayanaswamy-Moynihan relaxation model and microscopic crystal growth was proposed.

Neuroimaging of traumatic brain injury in military personnel: An overview

BACKGROUND

The incidence of blunt-force traumatic brain injury (TBI) is especially prevalent in the military, where the emergency care admission rate has been reported to be 24.6-41.8 per 10,000 soldier-years. Given substantial advancements in modern neuroimaging techniques over the past decade in terms of structural, functional, and connectomic approaches, this mode of exploration can be viewed as best suited for understanding the underlying pathology and for providing proper intervention at effective time-points.

APPROACH

Here we survey neuroimaging studies of mild-to-severe TBI in military veterans with the intent to aid the field in the creation of a roadmap for clinicians and researchers whose aim is to understand TBI progression.

DISCUSSION

Recent advancements on the quantification of neurocognitive dysfunction, cellular dysfunction, intracranial pressure, cerebral blood flow, inflammation, post-traumatic neuropathophysiology, on blood serum biomarkers and on their correlation to neuroimaging findings are reviewed to hypothesize how they can be used in conjunction with one another. This may allow clinicians and scientists to comprehensively study TBI in military service members, leading to new treatment strategies for both currently-serving as well as veteran personnel, and to improve the study of TBI more broadly.

Pathophysiology and Management of Intracranial Hypertension and Tissular Brain Hypoxia After Severe Traumatic Brain Injury: An Integrative Approach

Monitoring intracranial pressure in comatose patients with severe traumatic brain injury (TBI) is considered necessary by most experts. Acute intracranial hypertension (IHT), when severe and sustained, is a life-threatening complication that demands emergency treatment. Yet, secondary anoxic-ischemic injury after brain trauma can occur in the absence of IHT. In such cases, adding other monitoring modalities can alert clinicians when the patient is in a state of energy failure. This article reviews the mechanisms, diagnosis, and treatment of IHT and brain hypoxia after TBI, emphasizing the need to develop a physiologically integrative approach to the management of these complex situations.

The physiologic effects of indomethacin test on CPP and ICP in severe traumatic brain injury (sTBI)

BACKGROUND

Refractory intracranial hypertension (RICH) is associated with high mortality in severe traumatic brain injury (sTBI). Indomethacin (INDO) can decrease intracranial cerebral pressure (ICP) improving cerebral pressure perfusion (CPP). Our aim was to determine modifications in ICP and CPP following INDO in RICH secondary to sTBI.

METHODS

INDO was administered in a loading dose (0.8 mg/kg/15 min), followed by continuous 2-h infusion period (0.5 mg/kg/h). Clinical outcome was assessed at 30 days according to Glasgow Outcome Scale (GOS). Differences in ICP and CPP values were assessed using repeated-measures ANOVA. Receiver operating characteristic curve (AUC) was used for discrimination in predicting 30-day survival and good functional outcome (GOS 4 or 5). Analysis of INDO safety profile was also conducted.

RESULTS

Thirty-two patients were included. Median GCS score was 6 (interquartile range: 4-7). The most frequent CT finding was the evacuated mass lesion (EML) according to Marshall classification (28.1 %). Mortality rate was 34.4 %. Within 15 min of INDO infusion, ICP decreased (Δ%: -54.6 %; P < 0.0001), CPP increased (Δ%: +44.0 %; P < 0.0001), and the remaining was stable during the entire infusion period. Patients with good outcome (n = 12) showed a greater increase of CPP during INDO test (P = 0.028). CPP response to INDO test discriminated moderately well surviving patients (AUC = 0.751; P = 0.0098) and those with good functional recovery (AUC = 0.763; P = 0.0035) from those who died and from those with worse functional outcome, respectively. No adverse events were observed.

CONCLUSIONS

INDO appears effective in reducing ICP and improving CPP in RICH. INDO test could be a useful tool in identifying RICH patients with favorable outcome. Future studies are needed.

Effects of indomethacin test on intracranial pressure and cerebral hemodynamics in patients with refractory intracranial hypertension: a feasibility study

BACKGROUND

Intracranial hypertension is the final pathway of many neurocritical entities, such as spontaneous intracerebral hemorrhage (sICH) and severe traumatic brain injury (sTBI).

OBJECTIVE

This study aimed to (1) determine alterations in intracranial pressure (ICP) and cerebral hemodynamics after an indomethacin (INDO) infusion test and the related association with survival in patients with refractory intracranial hypertension (RICH) secondary to sICH or sTBI and (2) assess the safety profile after INDO.

METHODS

INDO was administered in a loading dose (0.8 mg/kg/15 min), followed by a 2-hour continuous infusion (0.5 mg/kg/h) in RICH patients with ICP greater than 20 mm Hg who did not respond to first-line therapies. Changes in ICP, cerebral perfusion pressure (CPP), and cerebrovascular variables (assessed by transcranial Doppler and jugular bulb saturation) were observed. Clinical outcome was assessed at 1 and 6 months according to the Glasgow Outcome Scale and correlated with INDO infusion test response. Analysis of INDO safety profile was conducted.

RESULTS

Thirteen sICH and 10 sTBI patients were studied. The median GCS score at admission was 6. Within 30 minutes of INDO infusion, ICP decreased (42.0 ± 13.5 vs 27.70 ± 12.7 mm Hg; Δ%: -48.4%; P < .001), and both CPP (57.7 ± 4.8 vs 71.9 ± 7.0 mm Hg; Δ%: +26.0%; P < .001) and middle cerebral artery velocity (35.2 ± 5.6 vs 42.0 ± 5.1 cm·s(-1); Δ%: +26.1%; P < .001) increased. The CPP response to a 2-hour INDO infusion test was correlated (R2 = 0.72, P < .001) with survival. No adverse events were observed after INDO.

CONCLUSION

Our findings support the effectiveness and feasibility of an INDO test in decreasing ICP and improving cerebral hemodynamics in surviving RICH patients. Future studies to evaluate different doses, lengths of infusion, and longer term effects are needed.

Increased intracranial pressure is associated with elevated cerebrospinal fluid ADH levels in closed-head injury

OBJECTIVES

Head injury frequently results in increased intracranial pressure and brain edema. Investigators have demonstrated that ischemic injury causes an increase in cerebrospinal fluid (CSF) levels of antidiuretic hormone (ADH); increased CSF ADH levels exacerbate cerebral edema, and inhibition of the ADH system with specific ADH antagonists reduces cerebral edema. The current study was designed to test the hypothesis that elevated levels of ADH are present in the CSF of subjects with head injury.

METHODS

Ventricular CSF and blood samples were taken from 11 subjects with head injury and 12 subjects with no known head trauma or injury. ADH levels were analyzed using radioimmunoassay. Severity of increased intracranial pressure (ICP) was rated in head-injured subjects using a four-point ordinal scale, based on which treatments were necessary to reduce ICP.

RESULTS

Subjects with head injury had higher CSF (3.2 versus 1.2 pg/ml; P<0.02) and plasma (4.1 versus 1.4 pg/ml; P<0.02) levels of ADH than did control subjects. In head-injured subjects, CSF ADH levels positively correlated with severity of ICP.

DISCUSSION

The results of this study suggest that ADH plays a role in brain edema associated with closed head injury.

Focus on therapy of primary stabbing headache

Primary stabbing headache (PSH) is a short-lasting but troublesome headache disorder, which has been known for several decades. The head pain occurs as a single stab or as a series of stabs generally involving the area supplied by the first division of trigeminal nerve. Stabs last for approximately a few seconds, occurring and recurring from once to multiple times per day in an irregular pattern. For the diagnosis of PSH, it is mandatory that any other underlying disorder is ruled out. Indomethacin represents the principal option in the treatment of PSH, despite therapeutic failure in up to 35% of the cases. Recent reports showed that cyclooxygenase-2 (COX-2) inhibitors, gabapentin, nifedipine, paracetamol and melatonin may also be effective. In this report, we focus on the therapy of PSH summarizing the information collected from a systematic analysis of the international literature over the period 1980–2009.

Lack of detrimental or therapeutic effects of cyclooxygenase inhibition in bile duct-ligated rats with hepatic encephalopathy

BACKGROUND

The pathogenetic mechanisms of hepatic encephalopathy (HE) are not fully understood. Cerebral blood flow regulated by cyclooxygenase (COX) may be involved in the development of HE. There are no comprehensive data concerning the effects of COX inhibition on HE in chronic liver disease.

METHODS

Male Sprague-Dawley rats weighing 240-270 g at the time of surgery were selected for experiments. Secondary biliary cirrhosis was induced by bile duct ligation (BDL). Those rats were then divided into two groups to receive i.p. injection of indomethacin (5 mg/kg per day) or distilled water for 7 days from day 36 to day 42 after BDL. The control group consisted of rats receiving a sham operation. Severity of encephalopathy was assessed by counts of motor activity. Plasma levels of tumor necrosis factor (TNF)-alpha and 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha)), and liver biochemistry tests were determined after treatment.

RESULTS

The motor activity in both groups of BDL rats were significantly lower than that of the control group (P < 0.001). As compared with the BDL rats treated with distilled water, BDL rats treated with indomethacin had significant lower levels of 6-keto-PGF(1alpha), but the motor activity, TNF-alpha levels and serum biochemistry tests were not significantly different between both BDL groups.

CONCLUSIONS

Chronic indomethacin administration did not have significantly detrimental or therapeutic effects on the severity of encephalopathy in BDL rats.

Pharmacological brain cooling with indomethacin in acute hemorrhagic stroke: antiinflammatory cytokines and antioxidative effects

We evaluated the effects of a novel pharmacological brain cooling (PBC) method with indomethacin (IND), a nonselective cyclooxygenase inhibitor, without the use of cooling blankets in patients with hemorrhagic stroke. Forty-six patients with hemorrhagic stroke (subarachnoid hemorrhage; n = 35, intracerebral hemorrhage; n = 11) were enrolled in this study. Brain temperature was measured directly with a temperature sensor. Patients were cooled by administering transrectal IND (100 mg) and a modified nasopharyngeal cooling method (positive selective brain cooling) initially. Brain temperature was controlled with IND 6 mg/kg/day for 14 days. Cerebrospinal fluid concentrations of interleukin-1beta (CSF IL-1beta) and serum bilirubin levels were measured at 1, 2, 4, and 7 days. The incidence of complicating symptomatic vasospasm after subarachnoid hemorrhage was lower than in non-PBC patients. CSF IL-1beta and serum bilirubin levels were suppressed in treated patients. IND has several beneficial effects on damaged brain tissues (anticytokine, free radical scavenger, antiprostaglandin effects, etc.) and prevents initial and secondary brain damage. PBC treatment for hemorrhagic stroke in patients appears to yield favorable results by acting as an antiinflammatory cytokine and reducing oxidative stress.

Posterior hypothalamic activation in paroxysmal hemicrania

OBJECTIVE

Paroxysmal hemicrania (PH) is a severe, strictly unilateral headache that lasts 2 to 30 minutes, occurs more than five times daily, is associated with trigeminal autonomic symptoms, and is exquisitely responsive to indomethacin. The purpose of the study was to determine the brain structures active in PH.

METHODS

Seven PH patients were studied using positron emission tomography (PET). Each patient was scanned in three states: (1) acute PH attack-off indomethacin; (2) pain-free-off indomethacin; and (3) pain-free after administration of intramuscular indomethacin 100 mg. The scan images were processed and analyzed using SPM99.

RESULTS

The study showed no significant activations during state 1 compared with state 2, but there was relative activation of the pain neuromatrix in both states 1 and 2 compared with state 3. This suggests that there is persistent activation of the pain neuromatrix during acute PH attacks and during interictal pain-free states off indomethacin that is deactivated by the administration of indomethacin. In addition, the untreated PH state was associated with significant activation of the contralateral posterior hypothalamus and contralateral ventral midbrain, which extended over the red nucleus and the substantia nigra.

INTERPRETATION

These activated subcortical structures may play a pivotal role in the pathophysiology of this syndrome.

The use of indomethacin in the treatment of plateau waves: effects on cerebral perfusion and oxygenation

Object. Plateau waves are sudden and steep increases in intracranial pressure (ICP) that can develop in patients with cerebral injuries, reduced pressure—volume compensatory reserve, and preserved autoregulation. They are caused by cerebral vasodilation in response to a reduction in cerebral perfusion and are associated with increased cerebral blood volume and reduced cerebral blood flow.

The authors evaluated the hypothesis that administration of indomethacin, a potent cerebral arteriolar vasoconstrictor, could interrupt the vicious cycle that occurs during plateau waves, extinguishing these waves and, ultimately, restoring cerebral perfusion and oxygenation.

Methods. Plateau waves developed in nine patients, seven with severe traumatic brain injury and two with intraparenchymal hemorrhage. One to four episodes of plateau waves per patient were treated with indomethacin (15–20 mg), which was delivered by an intravenous bolus injection. Each patient's mean arterial blood flow (MABP), ICP, cerebral perfusion pressure (CPP), and cerebral tissue PO2 were continuously monitored and the data obtained were stored in a personal computer. Each patient's jugular venous O2 saturation (SjvO2) and venoarterial difference in PCO2 were evaluated by intermittent blood sampling. During five episodes of plateau waves, middle cerebral artery flow velocities were evaluated by transcranial Doppler ultrasonography.

Indomethacin extinguished all plateau waves. On average, the ICP decreased from an initial value of 58.9 ± 11.6 mm Hg to 21.2 ± 8.6 and 25.8 ± 13.7 mm Hg after 5 and 10 minutes, respectively (p < 0.01). The MABP did not change significantly. As a consequence the CPP increased by 98 and 81% after 5 and 10 minutes, respectively (p < 0.01). Five and 10 minutes after indomethacin was administered, SjvO2 increased from an initial value of 50 ± 10.5% to 62 ± 7.6 and 59.9 ± 9.3%, respectively (p < 0.01); the cerebral tissue PO2 increased from an initial value of 13.4 ± 10.6 mm Hg to 23.6 ± 9.58 and 21.9 ± 9.2 mm Hg, respectively (p < 0.05); and the venous—arterial PCO2 decreased significantly. The mean and diastolic flow velocities increased significantly, whereas the pulsatility index decreased from 1.39 ± 0.56 to 1.09 ± 0.4 at 5 minutes and 1.06 ± 0.36 at 10 minutes (p < 0.05).

Conclusions. The findings confirm that plateau waves are caused by vasodilation and show that indomethacin, by constricting the cerebral arteries, is effective in extinguishing plateau waves, ultimately restoring cerebral perfusion and oxygenation.

Treatment of elevated intracranial pressure with indomethacin: friend or foe?

Indomethacin has been suggested as a therapeutic tool to manage elevated intracranial pressure in patients with severe head injury and patients undergoing craniotomy for brain tumors. Indomethacin is a non-selective cyclooxygenase inhibitor. Compared to other cyclooxygenase inhibitors indomethacin has unique effects on cerebral blood flow. Administration of indomethacin causes cerebral vasoconstriction and decreases cerebral blood flow, which elicits a decrease in intracranial pressure. The mechanism of indomethacin-induced cerebral vasoconstriction is not completely understood and controversies exist whether indomethacin causes cerebral ischemia. The primary aims of this article were to review the existing knowledge of indomethacin's influence upon cerebral hemodynamics and elevated ICP in patients with brain pathology. Furthermore, indomethacin's mechanism of action and whether it causes cerebral ischemia are discussed.

Oxidative stress in the pathogenesis of hepatic encephalopathy

The pathogenesis of hepatic encephalopathy (HE) remains elusive. While it is clear that ammonia is the likely toxin and that astrocytes are the main target of its neurotoxicity, precisely how ammonia brings about cellular injury is poorly understood. Studies over the past decade have invoked the concept of oxidative stress as a pathogenetic mechanism for ammonia neurotoxicity. This review sets out the arguments in support of this concept based on evidence derived from human observations, animal studies, and cell culture investigations. The consequences and potential therapeutic implications of oxidative stress in HE are also discussed.

Indomethacin-responsive headache syndromes

Indomethacin-responsive headache syndromes represent a unique group of primary headache disorders characterized by a prompt and often complete response to indomethacin to the exclusion of other nonsteroidal anti-inflammatory drugs and medications usually effective in treating other primary headache disorders. Because these headache disorders can easily be overlooked in clinical practice, they likely are more common than previously recognized. Indomethacin-responsive headache syndromes can be divided into several distinct categories: a select group of trigeminal-autonomic cephalgias, valsalva-induced headaches, and primary stabbing headache (ice-pick headache or jabs and jolts syndrome). Each category can be differentiated clinically and by the extent to which the individual headache disorders respond to indomethacin. The paroxysmal and continuous hemicranias invariably respond in an absolute manner to indomethacin, whereas valsalva-induced and ice-pick headaches may respond in an equally dramatic, but somewhat less consistent fashion. Hypnic headache recently has been described as another primary headache disorder that may respond to indomethacin.

Blood-brain barrier permeability to ammonia in liver failure: a critical reappraisal

In patients with acute liver failure (ALF), hyperammonemia is related to development of cerebral edema and herniation. The present review discusses the mechanisms for the cerebral uptake of ammonia. A mathematical framework is provided to allow a quantitative examination of whether published studies can be explained by the conventional view that cerebral uptake of ammonia is restricted to diffusion of the unprotonated form (NH(3)) (the diffusion hypothesis). An increase in cerebral blood flow (CBF) enhanced ammonia uptake more than expected, possibly due to recruitment or heterogeneity of brain capillaries. Reported effects of pH on ammonia uptake were in the direction predicted by the diffusion hypothesis, but often less pronounced than expected. The published effects of mannitol, cooling, and indomethacin in experimental animals and patients were difficult to explain by the diffusion hypothesis alone, unless dramatic changes of capillary surface area or permeability for ammonia were induced. Therefore we considered the possible role of membrane protein mediated transport of NH(4)(+) across the blood-brain barrier (BBB). Early tracer studies in Rhesus monkeys suggested that NH(4)(+) is responsible for 20% or even more of the transport of ammonia from plasma to brain. In other locations, such as in the thick ascending limb of Hendle's loop and in isolated astrocytes, transport protein mediated translocation of NH(4)(+) is predominant. Many of the ion-transporters involved in renal NH(4)(+) reabsorbtion are also present in brain capillary membranes and could mediate uptake of NH(4)(+). Astrocytic uptake of NH(4)(+) is associated with increased extracellular K(+), which is a potent cerebral vasodilator. Such interference between transport of NH(4)(+) and other cations could be clinically important because increased cerebral blood flow often precedes cerebral herniation in acute liver failure. We suggest that protein mediated transport of NH(4)(+) through the brain capillary wall is a realistic possibility that should be more intensely studied.

Is benign cough headache caused by intraocular haemodynamic aberration?

Rise of intracranial pressure (ICP) is currently presumed to underlie benign cough headache (BCH). Cough normally increases ICP but very few patients develop BCH. Children, young adults and females are rarely affected. Reduction of ICP by lumbar puncture (LP) or indomethacin offers variable therapeutic success. BCH can persist for several months or years but LP lowers ICP for few hours only and has significant morbidity. Choroidal blood volume and intraocular pressure (IOP) are instantaneously responsive to cough. Mechanical deformation of pressure-sensitive ocular structures by sudden experimental IOP elevation generates transient neural traffic in ocular trigeminal nerve fibres. Homeostatic mechanisms normally limit effect of cough-induced intraocular venous congestion. I propose that in a few patients, ocular sympathetic hypofunction significantly alters intraocular pressure-volume relation and predisposes to exaggerated choroidal venous congestion and fluctuation of IOP in response to cough, that, in turn, results in sudden transient cephalalgogenic antidromic trigeminal nerve discharge. Known variations in ocular hydrodynamics, ocular rigidity, and forced expiration rationalize epidemiology of BCH. This hypothesis can be tested by study of pupillary function and facial sweating in patients with BCH.

Neuroprotective effect from ischemia and direct free radical scavenging activity of Choto-san (kampo medicine)

Choto-san is a kampo medicine that is widely used in patients with cerebral infarction, but the details of its mechanism of action remain unclear. We examined the neuroprotective effects of Choto-san using an experimental cerebral ischemia model (i.e., a rat cardiac arrest model). We also investigated the ability of Choto-san to eliminate or inhibit the activity of free radicals. It was found that Choto-san significantly prevents delayed neuronal cell death after ischemic reperfusion. Electron spin resonance demonstrated that the formation of hydroxyl- and superoxide-DMPO spin adducts were inhibited by Choto-san. The results of this study indicated that Choto-san prevents delayed neuronal cell death in the hippocampal CA1 region after ischemia. Direct free radical scavenging activity is among the pharmacological effects of Choto-san.

Exertional, Cough, and Sexual Headaches

The International Headache Society applies the term exertional headache to head pain precipitated by exertion. The Society recognizes cough headache and sexual headache as distinct diagnoses. All three types of headache share characteristics and mechanisms, and together may be considered as headache provoked by exertional factors ( Table 1). In distinction to more typical headaches, such as tension-type headaches or migraine, HAPEF is brief, lasting seconds to minutes, and begins immediately following the precipitating exertion. Headache provoked by exertional factors may occur by itself, or in association with headaches that are not exertional. Secondary (or symptomatic) HAPEF arises as a result of an underlying disorder; primary (or benign) HAPEF has no underlying cause. Clinicians must consider HAPEF potentially serious until appropriate investigations are undertaken. Fortunately, disorders that underlie secondary headaches usually become apparent with examination or laboratory testing. Clinical features of the headaches may also offer a clue (Table 2). Several theories have been put forth to explain the underlying mechanism of exertional, cough, and sexual headache. The leading explanation regarding all three involves exertional factors leading to a sudden increase in intracranial pressure or an inappropriate reaction in the cerebral vasculature. Because exertion may also be a migraine trigger, neural hypersensitivity, similar to migraine, may also play a role in HAPEF. The literature contains only several small case studies that deal with treatment of exertional headache, and just one double blind, placebo-controlled study. The consensus to date is that secondary HAPEF resolves if the underlying illness can be treated; primary HAPEF responds well to prophylactic treatment. Treatment strategy varies little among headaches precipitated by cough, sex, or other forms of exertion. Avoidance strategies, sometimes combined with medication (particularly indomethacin), can effectively treat headaches produced by exertional factors in most cases.

Direct superoxide scavenging activity of nonsteroidal anti-inflammatory drugs: determination by electron spin resonance using the spin trap method

Nonsteroidal anti-inflammatory drugs (NSAIDs), which are used widely to manage pain, are known to inhibit cyclooxygenase, but details of the mechanisms of NSAID action remain unclear. We investigated the ability of three NSAIDs (indomethacin, loxoprofen, and etodolac) to eliminate and inhibit free radicals. Superoxide scavenging activity of these NSAIDs was measured in vitro by electron spin resonance spectrometry using 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) as a spin trap. Electron spin resonance demonstrated that formation of superoxide-DMPO spin adduct was completely inhibited by two nonselective cyclooxygenase inhibitors, indomethacin (3 mmol) and loxoprofen (3 mmol). The electron spin resonance study also demonstrated that the formation of superoxide-DMPO spin adduct was strongly inhibited by a selective cyclooxygenase-2 inhibitor, etodolac, in a concentration-dependent manner. These results indicate that NSAIDs, including indomethacin, loxoprofen, and etodolac, have direct superoxide scavenging activity.

Hypnic headache: another indomethacin-responsive headache syndrome?

Hypnic headache syndrome is a benign, recurrent, late-onset headache disorder that occurs exclusively during sleep. Lithium has been reported to be an effective treatment, but the side effects of this medication are sometimes prohibitive, particularly in the elderly. Other drugs have been reported to be effective in this disorder, including caffeine, flunarizine, and verapamil. Recently, indomethacin has been reported to effectively suppress hypnic headaches. We report the response of seven patients with hypnic headache who were treated with indomethacin. Hypnic headache syndrome appears to represent yet another headache disorder in which there is sometimes an impressive response to indomethacin.

Positive association between blood brain barrier disruption and osmotically-induced demyelination

Rapid correction of chronic hyponatremia can cause osmotic brain demyelination in animals and humans. Why demyelination develops is unknown, but blood brain-barrier disruption might expose oligodendrocytes to substances normally excluded from the brain. To test this hypothesis, chronic hyponatremia was induced and corrected using a new, reproducible rat model for producing osmotic brain demyelination. Blood brain barrier integrity was assessed by NMR imaging at either 3, 16 or 24 h during the first day of correction. Demyelination was determined histopathologically 5 - 6 days later. Of 96 rats studied, demyelination developed 5 - 6 days later in 37 rats, 89% of whom showed barrier disruption. In the 59 rats who did not develop demyelination, 45 (76%) had no barrier disruption. Thus, blood-brain barrier disruption during the first 24 h of correction was associated with a 70% risk of developing demyelination. By contrast, the risk of developing subsequent demyelination was only 8% when the barrier was intact. This strong association between barrier disruption and subsequent demyelination provides new insights into the role of blood brain barrier function in demyelinative disorders such as the osmotic demyelination syndrome and by extension to other demyelinative disorders such as multiple sclerosis.