Anatomic Study of Nutrient Foramina of Posterior Axis with Application to C2 Pedicle Screw Placement.

OBJECTIVE: Pedicle screws placed into C2 necessitate a thorough understanding of this bone's unique anatomy. Although multiple landmarks and measurements have been used by surgeons, these are often varied in the literature with no consensus. Herein, we studied one recently proposed landmark using the nutrient foramina of the posterior aspect of C2 for pedicle screw placement. METHODS: On 19 (38 sides) C2 dry bone specimens, the presence, size, location, and distance from the midline of the nutrient foramina found at the junction between the isthmus and lamina were documented and measured. In addition, to discern the source of the artery entering such foramina, an injected adult cadaver was dissected. RESULTS: The number of foramina ranged from 0-5 with a mean of 1.84. On 3 sides, no foramina were identified. The mean diameter of the foramina was 0.57 mm. The location of the foramina was at position 1 on 9.5% of sides, position 2 on 66.4% of sides, and position 3 on 24.1% of sides. The mean horizontal distance from the midline of the spinous process of C2 to the foramina was 25.17 mm. In the cadaveric specimen, the source of the artery entering these C2 nutrient foramina was found to be distal branches of the deep cervical artery. CONCLUSIONS: We found the nutrient foramina of the C2 laminae are useful for pedicle screw placement. However, there are minor variations of the number and position of these structures. Lastly, on the basis of our study, 7.9% (n = 3) of sides will not have such foramina.

Desmin-related myopathy with Mallory body-like inclusions is caused by mutations of the selenoprotein N gene.

Desmin-related myopathies (DRMs) are a heterogeneous group of muscle disorders, morphologically defined by intrasarcoplasmic aggregates of desmin. Mutations in the desmin and the alpha-B crystallin genes account for approximately one third of the DRM cases. The genetic basis of the other forms remain unknown, including the early-onset, recessive form with Mallory body-like inclusions (MB-DRMs), first described in five related German patients. Recently, we identified the selenoprotein N gene (SEPN1) as responsible for SEPN-related myopathy (SEPN-RM), a unique early-onset myopathy formerly divided in two different nosological categories: rigid spine muscular dystrophy and the severe form of classical multiminicore disease. The finding of Mallory body-like inclusions in two cases of genetically documented SEPN-RM led us to suspect a relationship between MB-DRM and SEPN1. In the original MB-DRM German family, we demonstrated a linkage of the disease to the SEPN1 locus (1p36), and subsequently a homozygous SEPN1 deletion (del 92 nucleotide -19/+73) in the affected patients. A comparative reevaluation showed that MB-DRM and SEPN-RM share identical clinical features. Therefore, we propose that MB-DRM should be categorized as SEPN-RM. These findings substantiate the molecular heterogeneity of DRM, expand the morphological spectrum of SEPN-RM, and implicate a necessary reassessment of the nosological boundaries in early-onset myopathies.