[Chronic myasthenia gravis mimicking muscular dystrophy, in eastern Colombia]. / Miastenia gravis crónica que simula distrofia muscular, en el oriente de Colombia.

INTRODUCTION. Myasthenia gravis is an apparently well-defined neuromuscular disease with some variants, including one recently described as chronic myasthenia gravis. CASE REPORT. We present a 22 year old Columbian woman who complained of progressive weakness for the previous four years, affecting her pelvic and shoulder girdles but with no clinical involvement of the extra-ocular muscles. Repetitive stimulation of the neuro-muscular junction of the abductor digiti quinti muscle was negative, but positive for myasthenia gravis in the trapezius muscle and the right orbital eye muscles. Her symptoms improved and the clinical neurophysiological studies were normal again after treatment with pyridostigimine, which confirmed the diagnosis.

[Prions, infections and confusions in the "transmissible" spongiform encephalopathies. The other evidence-based science. III. Review]. / Priones, infecciones y confusiones en las encefalopatías espongiformes "trasmisibles". Ciencia basada en la otra evidencia III. Revisión.

There are some neurological disorders with a pathological hallmark called spongiosis which include Creutzfeld-Jakob disease and its new variant, the Gertsmann-Straussler-Scheinker Syndrome and the Fatal Familial Insomnia in humans; and Scrapie and Bovine Spongiform Encephalopathy, among others, in animals. The etiological agent has been considered either transmissible or hereditary or both. Curiously, this agent has no nucleic acids, is impossible to filter, is resistant to inactivation by chemical means, has not been cultured and is unobservable at electron microscopy. All of these facts have led to some researches to claim that these agents are similar to viruses appearing in computers. However, after almost fifty years of research, is still not possible to explain why and how such elements produce the diseases commented about. On the contrary, during these years have been possible to know that these entities called slow viral infections, transmissible amyloidosis, transmissible dementia, transmissible spongiform encephalopathies or prion diseases appear in individuals with genetical predispositions exposed to several worldwide immunological stressors. The possibility that prions are the consequence and not the cause of these diseases in animals and man is day by day more reliable, and supports the suggestion that a systematic intoxication due to pesticides as well as mycotoxin ingestion, produced mainly by different molds such as Aspergillus, Penicillium or Fusarium, seem to be the true etiology of these neurodegenerative disorders.

[Anatomical and pathological study of the temporomandibular joint disk in Colombian individuals]. / Estudio anátomo-patológico del disco de la articulación temporomandibular en individuos colombianos.

BACKGROUND: The temporomandibular joint is an oval fibrous plate that completely divides the joint and accommodates irregularities existent in the bone articular surfaces. AIM: To study the frequency of temporomandibular joint disk abnormalities among Colombian subjects. MATERIAL AND METHODS: We studied 120 temporomandibular joint disks obtained from fresh cadavers arrived in the Instituto de Medicina Legal, in Cali Colombia. These were analyzed according to subject's dental status and age. RESULTS: Nineteen percent of disks had small erosions. In 7.5% of disks there were wider erosions or perforations. Twenty six percent of discs were very thin and this alteration was seen mostly in people aged 50 years or older. CONCLUSIONS: These results are intermediate between those who claim that disk perforations are rare and those who had shown tile opposite. The loss of dental pieces seems to be a risk factor leading to such disk perforation.

A re-evaluation of the mechanism of action of botulinum toxin on facial movement disorders in man.

Despite a lot of research aimed at clarifying the mechanism of action of botulinum toxin, mostly at supraspinal levels, a complete understanding of it is still elusive. However, recent investigations, including our own, allow us to suggest that, in facial muscles, the effects of botulinum toxin are not only in the neuromuscular junctions affecting the acetylcholine release but also modify the sensory inflow with subsequent changes on the muscle spindle-gammamotoneuron system.

Contralateral early blink reflex in multifocal motor neuropathy.

Multifocal motor neuropathy (MMN) is a clinical entity affecting the peripheral nerve system mainly. We present here a Colombian man, 37 year-old, who presented MMN, and interestingly, displayed abnormal responses in the blink reflex after electrical stimulation of the supraorbital nerves. These findings allow us to suggest that the lesion distribution in MMN mostly the subclinical one, seems to be more widespread than usually thought.

Recent concepts in the pathophysiology and evaluation of spasticity.

Spasticity is still a challenge to clinicians and scientists. The participation of Ia, Ib, II, III and IV afferents pathways, as well as those related with presynaptic inhibition. Renshaw cells modulation, and alpha and gamma motoneurons hyperexcitability, in this medical problem are reviewed. A brief overview on the more common neurophysiological tests performed during the evaluation of human spasticity is presented.

The effects of tobacco smoking on the short, middle, and long latency responses of the blink reflex in humans.

The three responses (R1, R2, and R3) of the electrically elicited blink reflex (BR) obtained in four normal human subjects were investigated before and after smoking both a filtered and an unfiltered cigarette. The changes observed in the BR were stronger and statistically more significant for the unfiltered than for the filtered cigarette, (p < 0.0001) and were more dramatic in R3 than R1 or R2. The action of nicotine on central pathways located at the interneuronal network of the brainstem, basal ganglia, and C fiber structures involved with this reflex seems to be the most likely mechanism for these findings.

Discrepancy, coincidence or evidence in chronic idiopathic spastic paraparesis throughout the world. A meta-analysis on 2811 patients.

HTLV-I has been associated with a chronic idiopathic spastic paraparesis (CHISPA) in man; however, a complete understanding of this association is still debated. We selected the most comprehensible papers on this topic between 1985 and 1996, and found that 1261 out of 2811 patients (44.9%) reported, throughout the world, were HTLV-I positive. The mean age was 39.5 years and there was a female predominance of 1.9:1. These results do not exclude the causality of HTLV-I as a germen associated to CHISPA; however, other causes (e.g., toxic, immunosuppressors) must be considered as participating in the multistep neurodegeneration observed in CHISPA throughout the world.

Multiple sclerosis and HTLV-I associated myelopathy/tropical spastic paraparesis are two distinct clinical entities.

Multiple sclerosis (MS) and HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) can overlap in their clinical features and thereby cause difficulties for clinicians in relation to diagnosis and therapy. However, epidemiological biochemical, immunological, virological and radiological studies point to a number of significant differences. Recent comparative neurophysiological data, including blink reflex studies, obtained in these disorders, is briefly reviewed here and provides additional evidence of difference. The abnormal blink reflex in patients with MS consist of prolonged latencies and absences of R1 and R2 responses and are mainly due to demyelinating lesions around the pans. In contrast, in HAM/TSP the blink reflex abnormalities frequently include an unusual early response, R1k, which is probably a consequence of interneuronal hyperexcitability around the brainstem. Thus these findings provide further support for our contention that HAM/TSP and multiple sclerosis are distinctly different both as clinical entities and in their underlying pathomechanisms.