RESUMEN
BACKGROUND: The diagnosis of Alzheimer's disease (AD) during life remains difficult and a definite diagnosis of AD relies on histopathological confirmation at post-mortem or by cerebral biopsy. It is well known that levels of tau proteins are consistently and significantly increased in the cerebrospinal fluid (CSF) of Alzheimer's patients versus levels in normal controls. However, the sole use of this biochemical marker as a test for AD is hampered by mediocre specificity, since tau concentrations may also be elevated in certain other neurological disorders (OND). Studies of the regional cerebral blood flow (rCBF) are widely performed because of their convenience and usefulness in a variety of neurological disorders. Most studies have reported high diagnostic accuracy for brain perfusion single-photon emission tomography (SPECT) in Alzheimer's disease. METHODS: In order to improve specificity, in this study, correlation of 99mTc-HMPAO SPECT scanning and CSF tau protein levels was made in 117 patients with AD, 67 patients with OND (26 of which had other dementias), and 23 age-matched controls. Means and standard deviations of tau protein levels were 297, 42 +/- 221, 12 in AD patients and 78, 07 +/- 98, 51 in patients with OND (p = 0.0006). No correlation was noted between CSF tau protein levels and age, duration of the disease, and neuropsychological scores of mini-mental state examination (MMSE), Cambridge Cognitive Examination (CAMCOG), and Functional Rating Scale for Symptoms of Dementia (FRSSD). FINDINGS: There was a bilateral parietal and temporal hypoperfusion in patients with AD in SPECT in comparison to normal subjects (p < 0.05) and there was a statistical correlation between this hypoperfusion and neuropsychological tests, such as MMSE and CAMCOG (p < 0.01). There was no correlation between tau protein levels and hypoperfusion in SPECT. INTERPRETATION: Conclusively, the correlation between elevated levels of tau proteins and hypoperfusion in SPECT in AD patients therefore cannot improve the specificity of tests in AD and this means that the determination of CSF tau proteins levels is not a specific diagnostic test for AD.
Asunto(s)
Enfermedad de Alzheimer/diagnóstico , Encéfalo/metabolismo , Cognición , Pruebas Neuropsicológicas/normas , Tomografía Computarizada de Emisión de Fotón Único , Proteínas tau/líquido cefalorraquídeo , Anciano , Enfermedad de Alzheimer/líquido cefalorraquídeo , Enfermedad de Alzheimer/diagnóstico por imagen , Enfermedad de Alzheimer/psicología , Biomarcadores/análisis , Encéfalo/irrigación sanguínea , Estudios de Casos y Controles , Circulación Cerebrovascular , Demencia/diagnóstico , Diagnóstico Diferencial , Femenino , Humanos , Masculino , Persona de Mediana Edad , Valor Predictivo de las Pruebas , Radiofármacos , Sensibilidad y Especificidad , Exametazima de Tecnecio Tc 99m , Factores de Tiempo , Tomografía Computarizada de Emisión de Fotón Único/métodosRESUMEN
The somatosensory evoked potentials (SEPs) and visual evoked potentials (VEPs) were studied in 19 patients with multiple sclerosis; 17 controls were studied during fever (38.0 degrees - 39.7 degrees C) and 2-3 days following return to normal temperature. The latencies of components N20 and P114 were measured and specified as abnormal when their value exceeded the standard deviation of the controls by 2.5 times. The corresponding criterion for the evaluation of the amplitude of components N20 and P114 was a reduction in amplitude of more than 50%. In the controls fever did not cause significant changes in evoked potentials. On the other hand, patients with multiple sclerosis showed abnormalities in evoked potentials during fever in a greater number of recordings (26 of SEPs and 33 of VEBs) than after return to normal temperature (19 and 27 respectively). In addition, the average latency of components N20 and P114 was clearly greater in the patients during fever (N20 = 29.5 +/- 5.2 ms and P114 = 143 +/- 18.1 ms) than after return to normal temperature (N20 = 6.6 +/- 3.5 ms and P114 = 134 +/- 16 ms). The amplitude of components N20 and P114 in patients during fever was clearly smaller than after return to normal temperature. These differences were statistically significant. Finally, in two patients, a decrease was found, during fever, in the conduction velocity of the peripheral somatosensory pathway from the median nerve to the wrist at Erb's point.