CAPSULAS DE CONOCIMIENTO ( EPILEPSIA)

SIGNOS LATERALIZADORES POSICTALES

Paresia posictal ( parálisis de Todd)

• La parálisis de Todd es uno de los datos lateralizadores más antiguos descritos en pacientes con epilepsia, y es siempre contralateral a la zona epileptogénica. Se debe a un agotamiento neuronal de las áreas motoras primarias, por aumento de los niveles de ácido láctico y disfunción cerebrovascular.

Afasia y disfasia posictal

• Lateraliza en 92% de los pacientes hacia el hemisferio dominante de lenguaje.

Frotar la nariz ( nose wiping)

• Frotarse l nariz durante los primeros 60 seg después de finalizada la crisis se observa en 53% de los pacientes con epilepsia del lóbulo temporal, y es ipsilateral al sitio de inicio de la crisis en 92%.

-------------------------------------------------------------------------------------------------------------------------------

La epilepsia es una de las enfermedades neurológicas más comunes, dado que afecta entre 0.5 y 2% de la población mundial. A los cinco años del diagnostico, hasta 20% de los pacientes epilépticos habrá presentado un episodio de estado epiléptico; éste es la manifestación inicial hasta en 30% de los casos.

---------------------------------------------------------------------------------------------------------------------------------

The systemic and CNS physiologic changes depends the type of seizure. For both absence and “complex partial seizures”, the patient may have a variety of autonomic alterations, including changes in pulse rate, sweating, salivation, pupillary dilatation, and incontinence. Generalized tonic-clonic are associated with an increase in blood pressure and pulse rate, increased autonomic nervous system activation, a metabolic acidosis, a drop in PO2 and increase in PCO2 during the apneic tonic phase, and rarely, hyperkalemia or rhabdomyolysis. Following an isolated generalized tonic-clonic seizure, these abnormalities usually return to baseline within an hour.

Durin a seizure, blood flow and glucose utilization in the brain ate increased. Accompanying the neuronal activity may be changes in lactate and PH, alterations in the concentration of neurotransmitters, and increase in extracelular potassium, and a decrease in extracelular calcium. Generalized tonic-clonic seizures and most “complex partial seizures” actívate the hypothalamus and increase serum prolactin, a finding that may help to differentiate epileptic from non epileptic seizures.

----------------------------------------------------------------------------------------------------------------------------------

Common Metabolic Causes of Seizures

Hypocalcemia                        Anoxia

Hyponatremia                       Nonketotic hyperglycemic states

Hypoglycemia                        Inherited metabolic disease

Liver failure                                       a. Aminoacidurias

Renal failure                                      b. Urea cycle disorders

---------------------------------------------------------------------------------------------------------------------------------- 

What are the four most common inherited epileptic syndroms?

1.     Febrile convulsions, 2. Benign childhood epilepsy with central temporal spikes,3. Childhood absence epilepsy, and 4. Juvenile myoclonic epilepsy. The first three síndromes usually are associated with seizures that remit spontaneously. Juvenile myoclonic epilepsy usually responds to treatment with valproate.

---------------------------------------------------------------------------------------------------------------------------------------

What is the value of PET scannong in patients with epilepsy?

Positron emission tomography (PET) scans have helped us to understand some of the metabolic changes that occur during seizures. PET scans demonstrate hypermetabolism or increased glucose uptake during the seizure. Most patients, however, are studied during the interictal period. In this setting, patients with epilepsy that have focal onset may show an área of hypometabolism in the región of seizure onset and a decrease in glucose uptake. PET scanning has been useful in helping to localize seizure onset in patients with intactable “complex partial seizure” that are being evaluated for surgical therapy.

----------------------------------------------------------------------------------------------------------------------------------
Desde el punto de vista fisiológico, lasa crisis epílepsticas se definen como una alteración repentina de la función del sistema nervioso central ( SNC) a causa de una descarga eléctrica paroxística de alta frecuencia, sincrónica de baja frecuencia o de alto voltaje.

Desde la perspectiva fisiológica más amplia se necesitan tres factores para que surjan crisis :

1. una población de neuronas patológicamente excitables
2. un incremento en la actividad glutaminérgica excitadora 
3. disminución de la actividad de las proyecciones gabaérgicas e inhibidoras.