Hyperbaric oxygen pretreatment according to the gas micronuclei denucleation hypothesis reduces neurologic deficit in decompression sickness in rats.

During sudden or too rapid decompression, gas is released within supersaturated tissues in the form of bubbles, the cause of decompression sickness. It is widely accepted that these bubbles originate in the tissue from preexisting gas micronuclei. Pretreatment with hyperbaric oxygen (HBO) has been hypothesized to shrink the gas micronuclei, thus reducing the number of emerging bubbles. The effectiveness of a new HBO pretreatment protocol on neurologic outcome was studied in rats. This protocol was found to carry the least danger of oxygen toxicity. Somatosensory evoked potentials (SSEPs) were chosen to serve as a measure of neurologic damage. SSEPs in rats given HBO pretreatment before a dive were compared with SSEPs from rats not given HBO pretreatment and SSEPs from non-dived rats. The incidence of abnormal SSEPs in the animals subjected to decompression without pretreatment (1,013 kPa for 32 min followed by decompression) was 78%. In the pretreatment group (HBO at 304 kPa for 20 min followed by exposure to 1,013 kPa for 33 min and decompression) this was significantly reduced to 44%. These results call for further study of the pretreatment protocol in higher animals.

Non invasive local cerebral oxygenation monitoring using a combination of light and ultrasound.

OBJECTIVES: We present a new imaging technology that will allow to obtain three-dimensional maps of oxygen saturation in the brain tissues. This technology is not invasive and not ionizing, and can lead to small, portable device that can be brought to bedside. METHODS: The technology uses a combination of near-infrared laser light and ultrasound. Like for other near-infrared spectroscopy techniques, light gives the information on the hemoglobin species present in the tissues. However, since tissues are turbid media, light alone cannot give precise local information. In the technique that we demonstrate, localization is obtained using a focussed ultrasound that locally shifts the laser wavelength, similarly to laser doppler techniques. The frequency-shifted light can be precisely detected and attributed without ambiguities to a specific location. By scanning the ultrasound focus, we can obtain a mapping of the oxygen saturation. RESULTS: We present preliminary results on a phantom showing the detection of an absorbing object buried more than two centimeters within the phantom. Scanning the ultrasound on the phantom allows to determine precisely the object position and absorption. Scattering and absorption parameters of the phantom are similar to the brain's. The probe works in the reflection mode, meaning that no transillumination is needed. The ultrasound frequency is 1.25 MHz, ensuring relatively good ultrasound penetration within the skull. CONCLUSIONS: The method is very promising for brain imaging of trauma or tumors. It is particularly suited for monitoring, since the use of the ultrasound removes the well-recognized problem of light propagation in the CSF.

Basilar vasospasm following spontaneous and traumatic subarachnoid haemorrhage: clinical implications.

BACKGROUND: Cerebral vasospasm has been commonly described following subarachnoid haemorrhage (SAH) though its impact on neurological outcome, especially in head trauma, has not been yet elucidated. The purpose of this study was to monitor and correlate neurological condition and flow velocities (FVs) in the arteries of the brain after SAH and more particularly to investigate the influence of basilar artery (BA) vasospasm on neurological outcome. METHODS: Daily transcranial Doppler (TCD) evaluations were conducted in 116 consecutive patients with subarachnoid haemorrhage. SAH was of traumatic origin (tSAH) in 59 patients and spontaneous (sSAH) in 57 patients. Vasospasm in the MCA and ACA was defined by a mean FV exceeding 120 cm/s and three times the mean FV of the ipsilateral ICA. Basilar artery (BA) vasospasm was defined as moderate whenever the FV was higher than 60 cm/s and severe above 85 cm/s. FINDINGS: Sixty-two patients (53.4%) had elevated FVs in the BA, among these 34 (29.3%) had FVs above 85 cm/s. Basilar vasospasm was significantly more common in tSAH (59.7%) than in sSAH (40.3%, P=0.041). In patients with moderate and severe BA vasospasm, FVs in the BA increased on the third day after admission and remained elevated for a week before returning to normal value by the end of the second week. This elevation in BA FVs in patients with BA vasospasm was followed by a significant and progressive worsening in the neurological condition at the end of the first week. Permanent neurological deficit was associated with elevated BA FVs consistent with moderate BA vasospasm whereas patients who remained in persistent vegetative state, had FVs consistent with severe BA vasospasm (P=0.00019). INTERPRETATION: The present results further support that BA vasospasm may act as an independent factor of ischaemic brain damage following SAH, especially in head trauma.

Excitatory and inhibitory corticospinal responses to transcranial magnetic stimulation in patients with minor to moderate head injury.

OBJECTIVES: The changes in excitatory and inhibitory responses to transcranial magnetic stimulation (TMS), as attested by motor evoked potential (MEP) and silent period (SP) parameters, were compared in patients who sustained minor to moderate head injury. METHODS: A total of 38 patients with brain concussion, and diffuse, focal, and combined brain injury and 20 healthy volunteers were examined. The MEPs and SPs were recorded from the abductor pollicis brevis muscle after single pulse TMS 2 weeks after head trauma. The parameters assessed were the MEP resting threshold, the MEP/M wave amplitude ratio, the central motor conduction time (CMCT), the SP threshold, the interthreshold difference (ITD), and the SP duration (SPD). RESULTS: The main finding was an increase in the ITD in patients with mild and moderate head injury due to the relatively greater augmentation of the MEP threshold. This was associated with a reduction of the MEP/M wave amplitude ratio. The degree of MEP and SP changes depended on severity of head injury and was not related to the type of brain lesions. The SPD did not differ significantly in brain concussion, or diffuse, focal and combined brain injury groups compared with the control group. The CMCT was prolonged in patients with diffuse and combined brain lesions. Among subjective complaints only fatigue was significantly related to ITD, MEP, and SP threshold abnormalities. CONCLUSIONS: The results suggest that mechanisms involved in MEP and SP generation are differently affected in head injury, the first being impaired more severely. The increase of the ITD accompanied by reduction of the MEP/M wave amplitude ratio may reflect a dissociated impairment of inhibitory and excitatory components of central motor control in head trauma.

Leeches for the unfortunate locksmith: self-inflicted posttraumatic transient cerebral blindness--mode of treatment and underlying mechanism (1826).

In 1826, Jean-Pierre Gama, a French military surgeon, treated a young locksmith who had self-inflicted posttraumatic transient cortical blindness. This may be the earliest detailed, firsthand description of this condition by a medically and scientifically trained observer. Gama's report sheds light on the concept of the mechanism of coup-contrecoup of cerebral concussion and its treatment in the early 19th century and on the germinating discipline of cerebral localization.

Neuropsychological effects of prefrontal slow rTMS in normal volunteers: a double-blind sham-controlled study.

Recent reports have suggested that repetitive transcranial magnetic stimulation (rTMS) is effective in major depression. Unlike ECT, rTMS does not involve a seizure and is associated with minimal side-effects, including cognitive difficulties. However, the effect of rTMS on cognitive functioning has not been systematically evaluated. This study was designed to examine the neuropsychological effects of slow rTMS in normal volunteers. Forty-six normal volunteers were randomly assigned to receive one session of right (N = 16) or left prefrontal (N = 15), or sham (N = 15) rTMS at 1 HZ. Patients were assessed before and after stimulation by a computerized neurospychological battery. All three groups showed significant improvement over time in processing speed (reaction time) and efficiency (correct responses per unit of time). However, no time by group interaction was found for any of the neuropsychological tests. These findings suggest that a single session of slow rTMS does not interfere with neurospychological functioning in normal volunteers, supporting clinical reports of no adverse cognitive effects.

[Favorable outcome of hyperacute epidural hematoma in an octogenarian].

Acute epidural hematoma is very rare in the elderly after head injury. It is usually associated with extremely high mortality or severe disability. In an 87-year-old woman a large, hyperacute, epidural hematoma was diagnosed. She was treated promptly and enjoyed an uneventful, complete recovery. This exceptional case should encourage an intensive approach even in seemingly minor head trauma in the elderly.

The blind beautiful eye.

Master Jehan Yperman, a medieval surgeon, observed that when the optic nerve is injured, the eye becomes blind and beautiful. This is an attempt to trace the footsteps of this forgotten surgeon and to track the history of the cosmetic use of the belladonna herb, as well as the concept of amaurotic mydriasis.

Brain natriuretic peptide and cerebral vasospasm in subarachnoid hemorrhage. Clinical and TCD correlations.

BACKGROUND AND PURPOSE: Hyponatremia has been shown in association with cerebral vasospasm (CVS) following aneurysmal subarachnoid hemorrhage (SAH). In the past few years there has been increasing evidence that brain natriuretic peptide (BNP) is responsible for natriuresis after SAH. The purpose of the present study was to investigate the relationship between BNP plasma concentrations and CVS after aneurysmal SAH. METHODS: BNP plasma concentrations were assessed at 4 different time periods (1 to 3 days, 4 to 6 days, 7 to 9 days, and 10 to 12 days) in 19 patients with spontaneous SAH. BNP plasma levels were investigated with respect to neurological condition, SAH severity on CT, and flow velocities measured by means of transcranial Doppler. RESULTS: Thirteen patients had Doppler evidence of CVS; 7 of these had nonsymptomatic CVS. In 6 patients, CVS was severe and symptomatic, with delayed ischemic lesion on CT in 5 of these. CVS was severe and symptomatic in 6 patients, and delayed ischemic lesions were revealed on CT in 5 of these. BNP levels were found to be significantly elevated in SAH patients compared with control subjects (P=0.024). However, in patients without CVS or with nonsymptomatic CVS, BNP concentrations decreased throughout the 4 time periods, whereas a 6-fold increase was observed in patients with severe symptomatic CVS between the first and the third periods (P=0.0096). A similar trend in BNP plasma levels was found in patients with severe SAH compared with those with nonvisible or moderate SAH (P=0.015). CONCLUSIONS: In conclusion, our results show that BNP plasma levels are elevated shortly after SAH, although they increase markedly during the first week in patients with symptomatic CVS. The present findings suggest that secretion of BNP secretion after spontaneous SAH may exacerbate blood flow reduction due to arterial vasospasm.

Classification of brain-stem trigeminal evoked potentials in multiple sclerosis, minor head injuries and post-concussion syndrome pathologies by similarity measurements.

In this study measurements obtained from brain-stem trigeminal evoked potentials (BTEP) are applied to the problem of diagnosing Multiple Sclerosis (MS) and Post-concussion syndrome (PCS). We present a simplistic model that depicts the BTEP waveform as the linear combination of a set of filters excited by a short stimulus. The relation between the BTEP latencies and the 1st to 4th harmonic components is shown. The performance of a fuzzy similarity measure based classifier is compared with that of human experts. The efficiency of the proposed classifier in conjunction with delay time and amplitude features is examined. Using this novel approach, a classification rate of 93.55% and 84.1% for MS and PCS pathologies, respectively, was achieved. This performance compares favorably to the classification rates of 84.28% for MS and 70.47% for PCS pathologies achieved by human experts.

Right prefrontal slow repetitive transcranial magnetic stimulation in schizophrenia: a double-blind sham-controlled pilot study.

BACKGROUND: The aim of this study was to extend our previous work on the therapeutic efficacy of repetitive transcranial magnetic stimulation (rTMS) in major depression to patients with schizophrenia. METHODS: Thirty-five inpatients with schizophrenia were randomly assigned to either right prefrontal rTMS or sham treatment and were rated before and after treatment for positive, negative, and depressive symptoms. RESULTS: Thirty-one subjects (rTMS = 16, sham = 15) completed a 2-week treatment protocol. No serious adverse effects were reported; however, rTMS was not superior to sham treatment on any of the clinical ratings. CONCLUSIONS: In contrast to our previous positive findings in major depression, right prefrontal slow rTMS does not appear to have a beneficial effect for actively psychotic patients with schizophrenia.

Penetrating head injuries caused by a new weapon, the side dome.

The "side dome" is a mix of high and low explosives with a multitude of small metal balls molded within a specially designed half-sphere that directs the explosion wave and the projectiles in one direction to augment the harm. This weapon, originally designed by guerrilla and terrorist groups, is now used by regular armies. This report presents one craniocervical and eight cranial injuries caused by this new weapon and discusses the cases' various clinical features, the paucity of intracerebral cavitation damage along the missile track, the need for only minimally aggressive surgery, and the relatively favorable outcome. In all cases, the helmet offered good protection and the entry of the projectiles was just below its rim in an upward direction.

Dissociation of somatosensory and motor evoked potentials in non-comatose patients after head injury.

OBJECTIVES: This study was performed to evaluate the clinical value of combined use of somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) in patients with different brain lesions after head trauma. METHODS: A total of 64 patients with minor and moderate head injury were investigated by means of SEPs recorded over the parietal and frontal areas and MEPs following single-pulse transcranial magnetic stimulation (sTMS) and slow-rate repetitive transcranial magnetic stimulation (rTMS). RESULTS: In almost 50% of the patients, a dissociated impairment of somatosensory and motor evoked potentials was found. This dissociation was related to different distribution of SEP and MEP abnormalities in head injury subgroups. The higher threshold to sTMS and increased variability of the MEP amplitude during slow-rate rTMS were the most prominent features in patients with focal brain contusions, suggesting impairment of the cortical excitability. SEP abnormalities, as well as central conduction impairments, were more noticeable in patients with diffuse brain injury. CONCLUSIONS: A combined analysis of SEPs and MEPs may improve the assessment of cortical dysfunctions and central conduction abnormalities in non-comatose patients with head injury. A slow-rate rTMS may be considered as a complementary technique to the evaluation of the threshold in assessment of the excitability of the motor cortex in minor and moderate head injury.

Therapeutic efficacy of right prefrontal slow repetitive transcranial magnetic stimulation in major depression: a double-blind controlled study.

BACKGROUND: Transcranial magnetic stimulation (TMS), a noninvasive technique for stimulation of the brain, has recently been suggested to be effective for the treatment of major depression. We conducted a double-blind, placebo-controlled study to assess the efficacy of slow repetitive TMS (rTMS) in patients with major depression. METHODS: Seventy patients with major depression (53 women, 17 men; mean age, 58.7 years; SD, 17.2 years) were randomly assigned to receive rTMS or sham rTMS in a double-blind design. Treatment was administered in 10 daily sessions during a 2-week period. Severity of depression was blindly assessed before, during, and after completion of the treatment protocol. RESULTS: All patients completed the first week of treatment and 67 completed the entire protocol. Patients who received rTMS had a significantly greater improvement in depression scores compared with those who received sham treatment. At the end of 2 weeks, 17 of 35 patients in the rTMS group, but only 8 of 32 in the sham-treated group, had an improvement of greater than 50% in their depression ratings. CONCLUSIONS: This controlled study provides evidence for the short-term efficacy of slow rTMS in patients with recurrent major depression. Additional studies will be necessary to assess the efficacy of rTMS as compared with electroconvulsive therapy as well as the long-term outcome of this treatment in major depression and possibly other psychiatric disorders.

[Exhaustion of motor cortex after head injury--revealed by transcranial magnetic stimulation].

We evaluated the pattern of motor evoked potentials elicited by single-pulse and slow-rate (1 Hz) repetitive, transcranial, magnetic stimulation (RTMS) in minor head injuries. The motor response to a single magnetic stimulus in patients with minor head injury was characterized by a significantly higher threshold than in healthy subjects. However, central and peripheral motor conduction was normal in all patients. A stable pattern of MEP throughout the RTMS session was the most prominent feature in the control group. A progressive decrease in MEP amplitude and irregular alternation of large and very small MEPs over the course of RTMS was observed in minor head injury. The higher threshold of the motor response and the abnormal patterns of MEP behavior revealed by RTMS may reflect impaired excitability and enhanced exhaustion of the motor cortex in patients with minor head injuries, which improve with time.

Indocyanine-green videoangiography of drusen as a possible predictive indicator of exudative maculopathy.

OBJECTIVE: Recent studies have shown that indocyanine-green videoangiography (ICG-V) is useful to image occult choroidal neovascularization. The authors studied the ICG-V findings in fellow drusen eyes of patients with unilateral exudative age-related macular degeneration (AMD). The authors also studied the occurrence of exudative changes to determine whether ICG-V is useful in predicting future exudative changes in these eyes with only drusen. DESIGN: Cohort study. PARTICIPANTS: The authors studied 432 consecutive patients diagnosed with unilateral exudative AMD in whom the fellow eye had only drusen by clinical fundus examination and fluorescein angiography. All of these eyes had ICG-V performed. Follow-up data were obtained in all eyes with abnormal indocyanine-green (ICG) angiograms and randomly sampled ICG angiograms of normal eyes. MAIN OUTCOME MEASURES: The initial ICG findings were classified as showing normal or abnormal hyperfluorescence. Abnormal hyperfluorescence eyes were subdivided into focal spots (focal areas of hyperfluorescence < 1 disc area in size) and plaques (areas of hyperfluorescence > 1 disc area). The development of exudative changes in eyes with normal and abnormal hyperfluorescence was compared. RESULTS: Of the 432 fellow eyes, 386 (89%) eyes with drusen had a normal ICG-V study, whereas 46 (10 focal spots and 36 plaques) (11%) eyes had an abnormal ICG-V. Exudative changes occurred in 6 (10%) of 58 normal ICG eyes and 9 (24%) of 38 eyes with abnormal ICG findings during a mean follow-up period of 21.7 months. The difference between drusen eyes with normal ICG angiograms and those with plaques on ICG-V regarding future exudative changes (10% vs. 27%, respectively) was statistically significant (P = 0.038). CONCLUSIONS: Abnormal ICG findings were found in 11% of eyes with clinically and fluorescein angiographically nonsuspicious drusen. The subgroup of patients with plaques on ICG-V had a higher chance of having exudative changes develop. Indocyanine-green videoangiography may be a predictive indicator of future exudative changes in eyes with drusen. A much larger prospective study seems justified.

Altered excitability of the motor cortex after minor head injury revealed by transcranial magnetic stimulation.

This study attempts to find out whether the motor evoked potential (MEP) elicited by single pulse and slow-rate (1 Hz) repetitive transcranial magnetic stimulation (TMS) can disclose concealed subclinical impairments in the cerebral motor system of patients with minor head injury. The motor response to single pulse TMS (STMS) of the patient group was characterized by significantly higher threshold compared with that of the control group. The central motor conduction time, as well as the peripheral conduction time were normal in all patients pointing to cortical impairment. Two main patterns of MEP changes in response to repetitive TMS (RTMS) were observed in the patient group. A.--progressive decrease of the MEP amplitude throughout the stimulation session to a near complete abolition. B.--irregularity of the amplitude and the waveform of the MEP in a chaotic form. The MEP latency remained stable during the whole stimulation session. The MEP abnormalities recovered gradually over the period of a few months. The higher threshold of the motor response to STMS and the abnormal patterns of the MEP to RTMS seem to reflect transient impairment of cortical excitability or "cortical fatigue" in patients who sustained minor head injures. Further study is needed to evaluated the extent and the pathophysiological mechanisms of the central nervous system fatigue phenomenon following head injury.