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How do the many etiologies of West syndrome lead to excitability and seizures? The corticotropin releasing hormone excess hypothesis

  • Kristen L Brunson
    Affiliations
    Department of Pediatrics, University of California at Irvine, Irvine, CA, 92697-4475, USA

    Department of Anatomy and Neurobiology, University of California at Irvine, Irvine, CA, 92697-4475, USA

    Department of Neurology, University of California at Irvine, Irvine, CA, 92697-4475, USA
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  • Mariam Eghbal-Ahmadi
    Affiliations
    Department of Pediatrics, University of California at Irvine, Irvine, CA, 92697-4475, USA

    Department of Anatomy and Neurobiology, University of California at Irvine, Irvine, CA, 92697-4475, USA

    Department of Neurology, University of California at Irvine, Irvine, CA, 92697-4475, USA
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  • Tallie Z Baram
    Correspondence
    Corresponding author. Tel.: +1-949-824-1063; fax: +1-949-824-1106
    Affiliations
    Department of Pediatrics, University of California at Irvine, Irvine, CA, 92697-4475, USA

    Department of Anatomy and Neurobiology, University of California at Irvine, Irvine, CA, 92697-4475, USA

    Department of Neurology, University of California at Irvine, Irvine, CA, 92697-4475, USA
    Search for articles by this author

      Abstract

      West syndrome (WS) is associated with diverse etiological factors. This fact has suggested that there must be a ‘final common pathway’ for these etiologies, which operates on the immature brain to result in WS only at the maturational state present during infancy. Any theory for the pathogenesis of WS has to account for the unique features of this disorder. For example, how can a single entity have so many etiologies? Why does WS arise only in infancy, even when a known insult had occurred prenatally, and why does it disappear? Why is WS associated with lasting cognitive dysfunction? And, importantly, why do these seizures – unlike most others – respond to treatment by a hormone, ACTH? The established hormonal role of ACTH in human physiology is to function in the neuroendocrine cascade of the responses to all stressful stimuli, including insults to the brain. As part of this function, ACTH is known to suppress the production of corticotropin releasing hormone (CRH), a peptide that is produced in response to diverse insults and stressors.
      The many etiologies of WS all lead to activation of the stress response, including increased production and secretion of the stress-neurohormone CRH. CRH has been shown, in infant animal models, to cause severe seizures and death of neurons in areas involved with learning and memory. These effects of CRH are restricted to the infancy period because the receptors for CRH, which mediate its action on neurons, are most abundant during this developmental period. ACTH administration is known to inhibit production and release of CRH via a negative feedback mechanism. Therefore, the efficacy of ACTH for WS may depend on its ability to decrease the levels of the seizure-promoting stress-neurohormone CRH.
      This CRH-excess theory for the pathophysiology of WS is consistent not only with the profile of ACTH effects, but also with the many different ‘causes’ of WS, with the abnormal ACTH levels in the cerebrospinal fluid of affected infants and with the spontaneous disappearance of the seizures. Furthermore, if CRH is responsible for the seizures, and CRH-mediated neuronal injury contributes to the worsened cognitive outcome of individuals with WS, then drugs which block the actions of CRH on its receptors may provide a better therapy for this disorder.

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