Normal and five-fingered hand: comparative X-ray morphometry in the post-natal age

BACKGROUND

Five-fingered hand (5-FH) with completely developed phalanges is a rare phenotype observed so far only in humans and characterised by three phalanges of the 1st ray. A long-lasting, debated question is if the missing element of the normal hand 1st ray is the metacarpal or the phalanx. In this study, comparative X-rays morphometry of long bones in normal and 5-FH is carried out with the aim to face this question through homology analysis of long bone segments in the transverse and longitudinal line of normal hand and 5-FH.

MATERIALS AND METHODS

In the normal hand X-rays (n =20) and in a 5-FH X-rays series (n = 9) the relative length of each segment on the ray total length and the index of growth rate (IGR) were assessed. The calculation of the first parameter in normal hand bi-phalangeal thumb was carried out on the 3rd ray total length in the same hand.

RESULTS

The parameters of relative length and the proximal/distal growth rate asymmetry in the post-natal period (assessed through the IGR) confirmed in 5-FH the homology of all the five segment on the transverse line. In the normal control hand, the relative length assessment methodology was biased by the missing segment of the thumb, therefore, the reference to the 3rd ray total length in the same hand (instead of the 1st), allowed the homology analysis of the thumb metacarpal and 1st phalanx with the lateral segments (2nd-5th ray) of the same hand. The 5-FH analysis was used to choose the more appropriate reference ray for the normal hand group.

CONCLUSIONS

The comparative analysis of relative lengths and IGRs in the two groups suggested homology of the (anatomical) 1st metacarpal with the 2nd-5th proximal phalanges in the same hand and that of the (anatomical) 1st proximal phalanx with the 2nd-5th mid phalanges. These data suggest that the missing segment of the normal hand thumb is the metacarpal.

Unilateral triple mandibular canal with double mandibular foramen: cone-beam computed tomography findings of an unexpected anatomical variant

The mandibular canal is a bony channel located within the spongiosa of the mandible. The main structure contained in the mandibular canal is the inferior alveolar nerve. The inferior alveolar nerve is a very important structure that requires due consideration during dental or surgical procedures involving the mandible. Therefore, a detailed morphological analysis of the mandibular canal should be carried out before any surgical procedure in the mandibular region in order to avoid complications and to reduce the risk of inadequate local nerve blocking. The human mandible typically has a single mandibular canal on each side; however, accessory mandibular canals have been described previously in the literature. The most common variant of the mandibular canal is the bifid mandibular canal, which has a prevalence ranging from 10% to 66% on cone-beam computed tomography (CBCT) examinations. A rare variant of bifid mandibular canal is the trifid canal, accounting for less than 6% of all bifid canals. In some cases, the bifid and trifid mandibular canals are associated with a double mandibular foramen, which is a rare anatomical variant with a reported incidence of 1.35% on CBCT images. Herein, we present the interesting CBCT images of an unexpected anatomical variant characterised by unilateral triple mandibular canal with double mandibular foramen in a young Caucasian woman.

Phenotype of five cases of prenatally diagnosed campomelic dysplasia harboring novel mutations of the SOX9 gene

OBJECTIVES

Campomelic dysplasia is a rare congenital skeletal disorder characterized by bowing of the long bones and a variety of other skeletal and extraskeletal defects, many of which can now be identified prenatally using advanced ultrasound equipment. The disorder is caused by mutations in SRY-box 9 (SOX9), a gene that is abundantly expressed in chondrocytes as well as in other tissues. However, the correlation between genotype and phenotype is still unclear. We report five cases of prenatally detected campomelic dysplasia in which the diagnosis was confirmed by molecular analysis.

METHODS

Ultrasound examinations were performed between 12 and 32 weeks. Standard fetal biometric measurements were obtained. Fetal sex was determined sonographically and confirmed by chromosomal analysis. Genomic DNA was obtained in four cases before termination of pregnancy from chorionic villi or amniocytes and in one case postnatally from peripheral blood.

RESULTS

Skeletal dysplasia, most often limb shortening and bowed femora, was observed in one case in the first trimester, in three cases in the second trimester and in one case, presenting late for antenatal care, in the third trimester. Four of the pregnancies were terminated and one was carried to term. Postmortem/postnatal physical and radiographic examinations confirmed the presence of anomalies characteristic of campomelic dysplasia. A de novo mutation in the SOX9 gene was detected in all four cases that underwent termination. The father of the proband in the case that went to term was a carrier of a somatic mosaic mutation without clinical or radiographic signs of campomelic dysplasia.

CONCLUSIONS

It is likely that the integrated expertise of ultrasonographers, obstetricians, pediatricians and clinical geneticists will markedly improve the likelihood of accurate prenatal clinical diagnoses of campomelic dysplasia. This will, in turn, encourage more specific molecular testing and facilitate comprehensive genetic counseling.

[The anatomy of the temporal region viewed by magnetic resonance]

The study of the temporal region has been improved by technologic progress from conventional radiography to linear tomography, then to pluridirectional tomography, CT and, finally, MRI. Twenty-five patients were examined with MRI--50 temporal regions in all. MRI was performed with a brain coil, SE T1-weighted sequences (TR 500 ms, TE 25 ms, FOV 180 mm, matrix 256 x 512, 2 acquisitions, slice thickness: 3 mm, acquisition time: 5.30 minutes) before and after Gd-DTPA administration. SE T2-weighted sequences (TR 2000 ms, TE 20-80 ms, FOV 180 mm, matrix 256 x 256, 1 acquisition, slice thickness: 4 mm, acquisition time: 8.30 minutes), 3D CISS sequences (TR 20 ms, TE 8 ms, FOV 180 mm, matrix 256 x 256, acquisition time: 2.46 minutes) and MRA 3D TOF TONE sequences (TR 33 ms, TE 8 ms, FOV 180 mm, matrix 256 x 256, acquisition time: 9.30 minutes) were performed. Neither the temporal bone, made of compact tissue, nor the air spaces (mastoid, antrum, middle ear cavity) exhibit any MR signal. On the contrary, the fluid filling the membranous labyrinth (endolymph and perilymph) and the cerebrospinal fluid filling the internal acoustic canal and the cerebello-pontine angle have high signal. This pattern allows a detailed study, unfeasible with CT, of the inner ear structures (cochlea, vestibule and semicircular canal) and of the internal acoustic canal. Moreover, MRI allows the whole VII and VIII cranial nerves to be studied from their origin at the brain stem to the internal acoustic porus and into the internal acoustic canal. Finally, MRI permits the noninvasive study of temporal region vessels. To conclude, MRI yields new anatomical details of the temporal region useful to address major diagnostic issues--e.g., labyrinth, internal acoustic canal and cerebello-pontine angle lesions.