When a sheep loses its tail, it cannot regenerate it in the manner of lizards. On the other hand, it is possible to clone mammals from somatic cells, showing that a complete developmental program is intact in a wounded sheep's tail the same way it is in a lizard. Thus, there is a requirement for more than only the presence of the entire genetic code in somatic cells for regenerative abilities. Thoughts like this have motivated us to assemble more than just a factographic synopsis on tissue regeneration. As a model, we review skin wound healing in chronological order, and when possible, we use that overview as a framework to point out possible mechanisms of how damaged tissues can restore their original structure. This article postulates the existence of tissue structural memory as a complex distributed homeostatic mechanism. We support such an idea by referring to an extremely fragmented literature base, trying to synthesize a broad picture of important principles of how tissues and organs may store information about their own structure for the purposes of regeneration. Selected developmental, surgical, and tissue engineering aspects are presented and discussed in the light of recent findings in the field. (Pediatr Res 63: 502-512, 2008)
A 38-year-old gravida 7 para 5 Hispanic woman at 36 weeks and 4 days gestation presented with a postpartum headache following vaginal delivery complicated by an unintentional dural puncture for epidural analgesia. Due to the positional nature of the headache and its frontal and occipital origin, a postdural puncture headache was diagnosed. After failure of conservative treatment, an epidural blood patch was used, which offered immediate relief. However, shortly following the procedure, the parturient's neurological condition deteriorated due to an unrecognized intraparenchymal and subarachnoid hemorrhage requiring an emergent craniectomy. This case highlights the importance of diligence when evaluating and treating postpartum headache despite a classic presentation. F orty percent of postpartum women have headaches, most of which occur in the fi rst week. Most causes of postpartum headaches are relatively benign, including migraines and tension headaches. Studies have demonstrated that the weeks following childbirth, known as the puerperium, are a particularly vulnerable time period for development of headaches of a variety of primary and secondary headache disorders, mainly due to hormonal, physiological, procedural, and psychological factors (1). Th is case highlights that the diagnosis of postpartum headache should be evaluated carefully, and secondary causes, that are potentially life threatening, should fi rst be ruled out before diagnoses of common causes are postulated. CASE DESCRIPTIONA 38-year-old gravida 7 para 5 Hispanic woman at 36 weeks and 4 days gestation with no signifi cant past medical history requested epidural analgesia for pain relief during augmented labor. Th e fi rst attempt at epidural catheter placement was complicated by dural puncture with a 17-gauge epidural needle, confi rmed by free fl ow of cerebrospinal fl uid. Th e second attempt at epidural catheter placement was successful, and continuous lumbar epidural analgesia was achieved and remained eff ective throughout the uneventful vaginal delivery.On the second postpartum day, the patient began to complain of a frontal headache and a verbal pain score of 6 to 10/10 that worsened in the upright position. Th e patient was initially normotensive with no focal neurological defi cits, and
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