Assessment of sensory function in neonatal sheep with somatosensory evoked potentials: methodology and normative data

C D Yingling  1 , C Meuli-Simmen, M Meuli, G B Timmel, N S Adzick, M Harrison

Fetal sheep are increasingly used as animal models for fetal surgical interventions such as repair of myelomeningocele. Since behavioral observations cannot provide objective information about preservation of sensory function, we have developed a technique for reliably recording somatosensory evoked potentials in neonatal sheep. We determined anatomic criteria for placement of recording electrodes over the somatosensory cortex using external landmarks, and recorded normative data for both ulnar and posterior tibial nerve stimulation in a series of normal neonatal sheep. The methodology and normative data are presented in this report; a companion paper demonstrates the utilization of this technique in a variety of experimental fetal interventions.

Journal: Pediatric Surgery International 15, 530-534 (1999)

Date: 01/11/1999

1 Department of Neurological Surgery, University of California, San Francisco, USA.

Experimental fetal neurosurgery: effects of in-utero manipulations on somatosensory evoked potentials

C D Yingling  1 , C Meuli-Simmen, M Meuli, G B Timmel, M Harrison, N S Adzick

Somatosensory evoked potentials (SEP) were used to objectively evaluate sensory function in neonatal sheep after experimental fetal surgery. Posterior tibial (PTN) and ulnar (UN) nerves were stimulated electrically and averaged SEP were recorded from scalp electrodes placed over the somatosensory cortex. Animals with experimentally-created myelomeningocele (MMC) showed no SEP to PTN stimulation, but normal SEP to UN stimulation. In-utero repair of the MMC resulted in preservation of neurologic function and normal PTN SEP. In-utero thoracic spinal-cord transection resulted in no regeneration, and no SEP to PTN stimulation. In-utero unilateral transection of the sciatic nerve, even with attempted repair, resulted in little or no regeneration and absent or grossly abnormal PTN SEP from the affected side. In summary, the SEP technique provides valuable information concerning preservation of sensory function in a variety of experimentally created neurologic abnormalities and can aid in functional evaluation of experimental therapeutic fetal interventions.

Journal: Pediatric Surgery International 15, 535-539 (1999)

Date: 01/11/1999

1 Department of Neurological Surgery, University of California, San Francisco, USA.

Altered smooth muscle development and innervation in the lower genitourinary and gastrointestinal tract of the male human fetus with myelomeningocele

E Shapiro  1 , M J Seller, H Lepor, D K Kalousek, G M Hutchins, E J Perlman, M Meuli

Purpose: We determine whether smooth and skeletal muscle or nerve density is altered in the lower genitourinary or gastrointestinal tract of male human fetuses with myelomeningocele at 20 weeks of gestation.

Journal: The Journal of Urology: 1998 Sep;160(3 Pt 2):1047-53; discussion 1079

Date: 01/09/1998

1 Department of Urology, New York University School of Medicine, New York, USA.

Spontaneous repair of superficial defects in articular cartilage in a fetal lamb model

R S Namba  1 , M Meuli, K M Sullivan, A X Le, N S Adzick

A fetal lamb model was developed to investigate the capacity of fetal articular cartilage for repair after the creation of a superficial defect. Superficial defects, 100 micrometers deep, were made in the articular cartilage of the trochlear groove in the distal aspect of the femur in eighteen fetal lambs that were halfway through the 145-day gestational period; the contralateral limb was used as a sham control. The wounds were allowed to heal in utero for three, seven, fourteen, twenty-one, or twenty-eight days. Seven days after the injury, the defects were filled with a hypocellular matrix, which stained lightly with safranin O. At twenty-eight days, the staining of the matrix was similar to that of the sham controls and the chondrocyte density and the architectural arrangement of the cell layers had been restored. An inflammatory response was not elicited, and no fibrous scar tissue was observed.

Journal: The Journal of Bone & Joint Surgery, American Volume: 1998 Jan;80(1):4-10

Date: 01/01/1998

1 Department of Orthopaedic Surgery, University of California at San Francisco, 94143-0728, USA.

Latissimus dorsi flap procedures to cover myelomeningocele in utero: a feasibility study in human fetuses

Claudia Meuli-Simmen a, b, c, d Martin Meuli a, b, c, d N. Scott Adzick a, b, c, d Michael R Harrison a, b, c, d

There is experimental and clinical evidence that in utero repair of myelomeningocele (MMC) may preserve neurological function. In five aborted human fetuses (gestational age, 18 to 29 weeks), the authors tested whether proximally and distally based latissimus dorsi flaps (LDF) can be used to cover MMC lesions. Fetal soft tissues were developed enough to allow surgical handling, preparation of both flap types was technically easy, and the vascular pedicles could be preserved. The proximally pedicled LDF was suitable to cover the upper spine from lower cervical to lower thoracic levels, whereas the distally pedicled LDF was suitable to cover the spine between lower thoracic and lower sacral levels. These results suggest that various LDF procedures are technically feasible in early gestational human fetuses and could be used for in utero repair of MMC.

Journal: Journal of Pediatric Surgery (Volume 32, Issue 8, Pages 1154-1156)

Date: 01/08/1997

a Division of Hand, Plastic, and Reconstructive Surgery, University Children's Hospital, Zurich, Switzerland.

b the Department of Surgery, University Children's Hospital, Zurich, Switzerland.

c The Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA, USA

d The Fetal Treatment Center, University of California, San Francisco, CA, USA