Determination of the Initial Abnormal Discharge Site in Temporal Lobe Epilepsy Through Combined EEG and Neuroimaging. What Is Next?

Objective: The objective of this study was to determine the relationship between atrophy of the hippocampus and severity of epilepsy in patients with temporal lobe epilepsy (TLE) as the first step to evaluate the possibility of surgery for epilepsy and analyze why patients cannot undergo epilepsy surgery. Methods: Volumetric MRI of the hippocampus was performed in 51 consecutive patients (29 men; mean age 40) with TLE. TLE diagnosis, lateralization, and severity (mild, moderate, severe) of seizures were based on a comprehensive evaluation that included neurologic examination and EEG in all patients. Patients with evidence of a lesion other than hippocampal sclerosis were not included in the study. We assessed the relationship between hippocampal volumes and electrophysiological evidence of seizure severity. Results: According to the affected side based on the EEG, a statistically significant difference (p < 0.001) in volume and a positive correlation between epilepsy and hippocampal atrophy were found. Conclusion: Our results confirm that volume loss to the hippocampus in patients with TLE correlates with the severity of epilepsy based on the EEG. Therefore, surgical treatment is considered early when hippocampal atrophy is evident in patients with refractory TLE. However, in Latin American countries, it is a challenge to get a patient to undergo epilepsy surgery. Therefore, we try to analyze the sad situation in our hospital.

Toxicity of cultured bullseye puffer fish Sphoeroides annulatus.

The toxin content in various life cycle stages of tank-cultivated bullseye puffer (Sphoeroides annulatus) were analyzed by mouse bioassay and ESI-MS spectrometry analysis. The presence of toxin content was determined in extracts of sperm, eggs, embryo, larvae, post-larvae, juvenile, pre-adult, and adult fish, as well as in food items used during the cultivation of the species. Our findings show that only the muscle of juveniles, the viscera of pre-adults, and muscle, liver, and gonad of adult specimens were slightly toxic (<1 mouse unit). Thus, cultivated S. annulatus, as occurs with other cultivated puffer fish species, does not represent a food safety risk to consumers. This is the first report of toxin analysis covering the complete life stages of a puffer fish under controlled conditions.

Activity-dependent slowing properties of an unmyelinated low threshold mechanoreceptor in human hairy skin.

It has been previously shown that unmyelinated afferent fibres in human skin are differentiated not only by their receptor characteristics, but also by their profiles of activity-dependent slowing. One type of profile, described originally as 'type 3', is different from that of nociceptors (type 1), cold afferents (type 2) and sympathetic efferents (type 4), in that these fibres display a minimal activity-dependent slowing (∼1% at 2 Hz). However, their function remains to be determined. Here we describe one unit with a typical 'type 3' activity-dependent slowing profile recorded from an undamaged fascicle of the superficial peroneal nerve of a patient. Its conduction velocity was 1.8 m s(-1) and it slowed by 1.3% during the 2 Hz tetanus. This unit had a mechanical receptive field in the hairy skin and responded readily to weak mechanical stimuli, and not to cold. This suggests that the low threshold unmyelinated mechanoreceptors recently described in human hairy skin are probably endowed with a 'type 3' activity-dependent profile.

Neuropathic pain syndrome displayed by malingerers.

Among 237 patients communicating chronic pain, associated with sensory-motor and "autonomic" displays, qualifying taxonomically for neuropathic pain, there were 16 shown through surveillance to be malingerers. When analyzed through neurological methods, their profile was characteristically atypical. There were no objective equivalents of peripheral or central processes impairing nerve impulse transmission. In absence of medical explanation, all 16 had been adjudicated, by default, the label complex regional pain syndrome (CRPS). The authors emphasize that CRPS patients may not only harbor unrecognized pathology ("lesion") of the nervous system (CRPS II), hypothetical central neuronal "dysfunction" (CRPS I), or conversion disorder, but may display a recognizable simulated illness without neuropsychiatric pathology.

A search for activation of C nociceptors by sympathetic fibers in complex regional pain syndrome.

OBJECTIVE: Although the term 'reflex sympathetic dystrophy' has been replaced by 'complex regional pain syndrome' (CRPS) type I, there remains a widespread presumption that the sympathetic nervous system is actively involved in mediating chronic neuropathic pain ["sympathetically maintained pain" (SMP)], even in the absence of detectable neuropathophysiology. METHODS: We have used microneurography to evaluate possible electrophysiological interactions in 24 patients diagnosed with CRPS I (n=13), or CRPS II (n=11) by simultaneously recording from single identified sympathetic efferent fibers and C nociceptors, while provoking sympathetic neural discharges in cutaneous nerves. RESULTS: We assessed potential effects of sympathetic activity upon 35 polymodal nociceptors and 19 mechano-insensitive nociceptors, recorded in CRPS I (26 nociceptors) and CRPS II patients (28 nociceptors). No evidence of activation of nociceptors related to sympathetic discharge was found, although nociceptors in six CRPS II patients exhibited unrelated spontaneous pathological nerve impulse activity. CONCLUSIONS: We conclude that activation of nociceptors by sympathetic efferent discharges is not a cardinal pathogenic event in either CRPS I or CRPS II patients. SIGNIFICANCE: This study shows that sympathetic-nociceptor interactions, if they exist in patients communicating chronic neuropathic pain, must be the exception.

Anti-inflammatory activity of superoxide dismutase obtained from Debaryomyces hansenii on type II collagen induced arthritis in rats.

INTRODUCTION: Rheumatoid arthritis is an autoimmune inflammatory disease of unknown etiology, free radicals have been implicated in the genesis and perpetuation of damage in this pathology. OBJECTIVE: To evaluate the anti-inflammatory effect of Cu,Zn-superoxide dismutase (SOD) obtained from two different sources (bovine erythrocytes, Be-SOD, and Debaryomyces hansenii, Dh-SOD) with Type II Collagen-induced Arthritis model in rats. MATERIAL AND METHODS: Arthritis was induced by repeated injection of a porcine type II collagen-incomplete Freund adjuvant suspension on the back of Dark Augui (DA) rats. Arthritis was clinically evaluated throughout the study. Body weight was determined at three different times. Two different doses for each treatment (Be-SOD, Dh-SOD) were tested: 100 and 1,000 U/kg. At the end of the trial (day 28), histological analyses of the most inflamed ankle joint, as well as serum anti-collagen antibodies, were determined. RESULTS: Both sources of SOD decreased, although to a different extent, the incidence and severity of the disease. Arthritis score was lower in all treatments, except for the low dose of Be-SOD. Groups receiving either source of SOD showed a significant weight increase compared to the placebo group. Histological damage was similar in all groups. Only the group that received the highest dose of Dh-SOD showed a significant lower antibody titer; nevertheless, no correlation appears to derive from arthritis score and antibody titer. CONCLUSION: Our findings suggest that, although unable to counteract the arthritis syndrome, SOD may still be beneficial due to its anti-inflammatory activity. In the case of Dh-SOD, the best effect was observed at the highest dose tested.

Toxic and harmful marine phytoplankton and microalgae (HABs) in Mexican Coasts.

Harmful Algal Blooms (HABs) are becoming an increasing problem to human health and environment (including effects on natural and cultured resources, tourism and ecosystems) all over the world. In Mexico a number of human fatalities and important economic losses have occurred in the last 30 years because of these events. There are about 70 species of planktonic and non-planktonic microalgae considered harmful in Mexican coasts. The most important toxin-producing species are the dinoflagellates Gymnodinium catenatum and Pyrodinium bahamense var. compressum, in the Mexican Pacific, and Karenia brevis in the Gulf of Mexico, and consequently the poisonings documented in Mexico are Paralytic Shellfish Poisoning (PSP) and Neurotoxic Shellfish Poisoning (NSP). Although there is evidence that Amnesic Shellfish Poisoning (ASP), Diarrhetic Shellfish Poisoning (DSP) and Ciguatera Fish Poisoning (CFP) also occur in Mexico, these problems are reported less frequently. The type of phytoplankton and epiphytic microalgae, their toxins and harmful effects as well as current methodology used to study these phenomena are presented in this paper. As an experienced group of workers, we include descriptions of monitoring and mitigation programs, our proposals for collaborative projects and perspectives on future research.

Hyperexcitable polymodal and insensitive nociceptors in painful human neuropathy.

Six patients with chronic pain, mechanical and thermal hyperalgesia/allodynia, and cutaneous vasodilatation starting distally in their extremities, were evaluated using clinical and neurophysiological methods and microneurography. Evidence of small-fiber polyneuropathy was documented in all, but the etiology remained cryptogenic in several. Different forms of hyperexcitability were detected by microneurography in both common polymodal and mechanically insensitive C nociceptors, which explain all the somatosensory abnormalities. Signs of hyperexcitability included reduced receptor threshold (accounting for mechanical and heat allodynias), spontaneous C nociceptor discharge (explaining spontaneous "burning" pain and antidromic vasodilatation), and multiplied nociceptor responses to stimulation (accounting for hyperalgesia). The clinical and electrophysiological profiles of these patients resemble the experimental syndrome evoked by application of capsaicin to the skin. This similarity, and the striking heat dependence of the spontaneous pain, suggest that a common feature may be altered expression or modulation of vanilloid 1 receptor, provoking abnormal nociceptor discharges.

Interactions between sympathetic vasoconstrictor outflow and C nociceptor-induced antidromic vasodilatation.

The interaction between orthodromic sympathetic vasoconstrictor and antidromic vasodilator effects of C-fiber stimulation was studied in normal human volunteers. Excitation of C fibers was achieved through administration of intermittent painful intraneural microstimulation to upper limb nerves, while recording cutaneous thermal emission profiles in the projected fields of cutaneous sensation. During initial stimulation, when both systems are co-activated, skin temperature decreased. Temperature increased after termination of the stimulus. Eventually, temperature decreased again upon renewed stimulation. Thus, sympathetic vasoconstriction was found to override the antidromic vasodilator effect induced by stimulation of C nociceptors. When interpreting abnormal deviations of skin temperature in patients with peripheral nerve disorders, the dynamic interplay between opposing vasomotor effects driven by sympathetic and somatic systems must be taken into consideration.

Thermographic observations on rats with experimental neuropathic pain.

Infrared thermographic images were obtained from the plantar hind paws of rats with an experimental nerve injury that produces signs of neuropathic pain. Thermograms confirmed that the experimental neuropathy produces signs resembling those of patients with neuropathic pain. The hind paws on the nerve-damaged side were abnormally hot, abnormally cold, or apparently normal 8-16 days post injury, a variability that is seen clinically in neuropathic pain patients. Abnormally cold hind paws became warm as soon as the injured sciatic nerve was transected, indicating that the underlying vasoconstriction was mediated by neural impulse activity. Xylazine (Rompun), a sympatho-inhibitory alpha 2-adrenoceptor agonist that normally increases cutaneous temperature, caused the hind paw on the control side to warm, as anticipated, while causing paradoxical cooling of abnormally hot hind paws, and even of 'normal temperature' paws on the nerve-injured side. These findings shed light on possible mechanisms underlying abnormal deviations of skin temperature as a symptom of nerve injury. The findings also attest to the usefulness of the experimental animal model of neuropathic pain and of the thermographic method.