J Hassanali

Ages of eruption of the permanent teeth in Kenyan African and Asian children

Mean ages of eruption of the permanent teeth (except 3rd molars) in African and Asian children were derived from a cross-sectional study of 2847 children aged 4-14 years, in selected nursery and primary schools in Nairobi, Kenya. Except for the premolars, the mandibular teeth erupted earlier than the maxillary ones in both races. The mandibular incisors and canines erupted earlier by 0.9-1.1 yr in Africans and 0.6-0.8 yr in Asians, and the molar by 0.2-0.4 yr in both races. The maxillary premolars were ahead of mandibular premolars by 0.1-0.2 yr in both races. The females were ahead of males in both races. Compared with the Asians, the African permanent teeth erupted earlier by 0.2-0.7 yr. The most frequent order of eruption in Africans is Mand I1, Mand M1, Max M1, Mand I2, and Max I1 between 5-7 years, while in the Asians the most frequent order is Mand M1, Mand I1, or Max M1, Max I1 and Mand I2 between 6-8 years. The incidence of Cusp of Carabelli in Africans and Asians is about 19-25%.

The third permanent molar eruption in Kenyan Africans and Asians

Data on third permanent molar eruption was obtained from a cross-sectional study of 1343 African and 1092 Asian students aged 13-23 years attending various schools in Nairobi and the University of Nairobi, Kenya. Africans are significantly ahead of the Asians in third molar emergence. As seen from the median age of eruption, in Africans mandibular molars emerge at 17.6-18.3 years followed by the maxillary at 18.5-18.9 years, while in the Asians mandibular molars emerge at 19.9-20.3 years and maxillary at 20.7-21.0 years. African females appear to be earlier than the males in median age of eruption by 0.3-0.4 years, while the Asian females tend to be later than the males by about 0.3 years, but these differences are not significant. Third molar emergence starts earlier in Africans at 13 years of age, and by 18.5 years 50% of Africans have all four molars present. In the Asians, third molar emergence begins at about 15 years and by 21.5 years 50% have all four molars present.

Anatomy and prevalence of atlas vertebrae bridges in a Kenyan population: An osteological study

Atlas bridges are bony outgrowths over the third segment of the vertebral artery. They may exist as incipient, incomplete, or complete bridges, converting the groove into a deep sulcus, incomplete, or complete foramen respectively. These bridges and their associated foramina display bilateral and sex differences in their prevalence and type. Occurrence of these bridges may predispose to vertebrobasilar insufficiency and Barre–Lieou syndrome. The coexistence of lateral and posterior bridges as well as side predilection is not clear in either sex. Their relative occurrence may also point to some evolutionary patterns. We studied the prevalence, side predilection, coexistence, and anatomical features of atlas bridges using 102 dry atlases (49 males and 53 females) obtained from the osteology department of the National Museums of Kenya. Complete posterior bridges occurred in 14.7% and 13.7% on the right and left sides, respectively. A lateral bridge was found in 3.9% of cases on the right side only. There was positive correlation in the coexistence of the bridges. A retrotransverse foramen was found in 13% of cases. This study has found that posterior and lateral atlas bridges occur in association especially on the right side. Complete bridges were more prevalent in females and were more often present on the right side. This pattern seems to mirror the sexual predilection of vertebral artery compression syndromes. Gender roles may have an influence on the occurrence of these bridges and therefore the syndromes as well. Clin. Anat. 23:649–653, 2010.

Comparative functional structure of the olfactory mucosa in the domestic dog and sheep

Olfactory acuity differs among animal species depending on age and dependence on smell. However, the attendant functional anatomy has not been elucidated. We sought to determine the functional structure of the olfactory mucosa in suckling and adult dog and sheep. Mucosal samples harvested from ethmoturbinates were analyzed qualitatively and quantitatively. In both species, the olfactory mucosa comprised olfactory, supporting and basal cells, and a lamina propria containing bundles of olfactory cell axons, Bowmans glands and vascular elements. The olfactory cells terminated apically with an expanded knob, from which cilia projected in a radial fashion from its base and in form of a tuft from its apex in the dog and the sheep respectively. Olfactory cilia per knob were more numerous in the dog (19 ± 3) compared to the sheep (7 ± 2) (p<0.05). In the dog, axonal bundles exhibited one to two centrally located capillaries and the bundles were of greater diameters (73.3 ± 10.3 μm) than those of the sheep (50.6 ± 6.8 μm), which had no capillaries. From suckling to adulthood in the dog, the packing density of the olfactory and supporting cells increased by 22.5% and 12.6% respectively. Surprisingly in the sheep, the density of the olfactory cells decreased by 26.2% while that of the supportive cells showed no change. Overall epithelial thickness reached 72.5 ± 2.9 μm in the dog and 56.8 ± 3.1 μm in the sheep. These observations suggest that the mucosa is better structurally refined during maturation in the dog than in the sheep.

Anatomic position of the asterion in Kenyans for posterolateral surgical approaches to cranial cavity.

The asterion, defined as the junction between lambdoid, parietomastoid, and occipitomastoid sutures, has been used as a landmark in posterolateral approaches to the posterior fossa. Its reliability however has been put into question due to its population‐specific variability in position, using external palpable landmarks and its relation to the transverse–sigmoid sinus complex. This study aimed at determining the anatomic position of the asterion in a Kenyan population. Measurements from the asterion to the root of zygoma and the tip of mastoid process, respectively were taken on both left and right sides of 90 (51 male, 39 female) human skulls. The relation of the asterion to the transverse–sigmoid sinus junction was also determined. The distances on the right and left sides from the asterion to the root of the zygoma were 58.85 ± 2.50 mm and 58.44 ± 2.12 mm, respectively. The asterion was 47.89 ± 3.72 mm above the tip of mastoid process on the right side and 47.62 ± 2.87 mm on the left side. This point was significantly higher in males (48.36 ± 2.72 mm) than in females (46.62 ± 3.37 mm) with a P‐value of 0.041. Regarding its position from the transverse–sigmoid sinus junction, it was at the junction in 72 cases, below it in 17 cases (average 3.68 mm) and only one case had the asterion above this junction (2.57 mm). The asterion therefore can reliably be ascertained using the parameters from the root of the zygoma and the tip of the mastoid process. The safest approach would be posteroinferior to the asterion so as to avoid lacerating the transverse–sigmoid sinus complex. Clin. Anat. 23:30–33, 2010.

Quantitative and somatotopic mapping of neurones in the trigeminal mesencephalic nucleus and ganglion innervating teeth in monkey and baboon

Neurones of the trigeminal mesencephalic nucleus (Mes V) and ganglion innervating the periodontium of incisor, canine and molar teeth in 10 monkeys and 10 baboons were counted and mapped using the horseradish peroxidase (Hrp), retrograde axonal transport method. Periodontal afferent neurones of all these teeth were well represented in the Mes V, although the incisors had a significantly higher number of labelled neurones than the canines or molars. The primary cell bodies of the periodontal afferents were located mainly in the caudal part of the ipsilateral Mes V from the level of the inferior colliculus to the floor of the fourth ventricle in the pons. The caudal periodontal Mes V neurones may be favourably located to make collateral connections with the trigeminal motor nucleus for jaw reflexes. Incisors and canines had a large and predominantly ipsilateral representation of Hrp-labelled neurones in the ganglion. In contrast, molar representation in the ganglion was sparse and all labelled neurones supplied ipsilateral teeth. The maxillary and mandibular teeth had a somatotopic distribution within the respective maxillary (middle) and mandibular (posterolateral) compartments of the trigeminal ganglion. It is suggested that the anterior teeth with greater connections to the Mes V and the ganglion may impart greater sensory perception and be involved in jaw reflexes to ensure a good occlusal relation during mastication, while the afferent connections of the molars may initiate complex jaw reflexes during the occlusal phase of mastication.

Anatomic Position of the Pterion among Kenyans for Lateral Skull Approaches

La pterion es un punto de confluencia sutural visto en la norma lateral del craneo, donde se unen los huesos frontal, parietal, temporal y esfenoides. La posicion del pterion exhibe variaciones en la poblacion. La ubicacion de este punto es importante en abordajes quirurgicos a las fosas craneales anterior y la media. Mediciones especificas se han realizado en ambos lados de 90 craneos humanos Kenyanos (51 varones, 39 mujeres). Las distancias desde el centro de pterion a la sutura frontocigomatica fue de 38,88+3,49 mm en el lado derecho y 38,24+3,47 mm en el lado izquierdo. El pterion fue ubicado 30,35+3,40 mm y 30,34+4,34 mm por encima del punto medio del arco cigomatico en los lados derecho e izquierdo, respectivamente. Los hombres presentaron un pterion estadisticamente significativo superior en comparacion con las mujeres, siendo de 39,31+3,28 mm y 37,35+2,97 mm por encima del punto medio del cigoma, respectivamente. La sutura frontocigomatica y el punto medio del cigoma pueden ser utilizados como referencia fiables para localizar a el pterion. Esta informacion puede ser util en la planificacion previa a la cirugia, sobre todo cuando los equipos dispositivos de neuronavegacion son escasos.

Estimation of calendar age from eruption times of permanent teeth in Kenyan Africans and Asians

Eruption data for permanent teeth, obtained from a previous cross-sectional study of 2847 African and Asian school children aged 4-14 years in Nairobi, Kenya, were used to calculate the median age and the 10th-90th percentile range of age, for a given number of teeth present. For a limited period (5-13 years) up to the time of eruption of second molars, the total number of permanent teeth erupted can be used to estimate the age of a child, with an error which increases with the number of teeth present. The range of this error is about 18-30% of the median age for African males, 21-29% for African females, 15-33% for Asian males and 18-33% for Asian females, with a 1 in 5 chance that the error may exceed these limits.

Morphometry and Variations of Bony Ponticles of the Atlas Vertebrae (C1) in Kenyans

Puentes del atlas, sobrecrecimientos oseos en el tercer segmento de la arteria vertebral se asocian con la compresion de la arteria y los nervios. Hay pocos estudios que comparan la morfometria de los puentes completos del atlas y el foramen transversal ipsilateral. Diferencias bilaterales y de genero en la morfometria de los puentes completos permanecen relativamente inexplorados. Ciento dos vertebras atlas (49 hombres y 53 mujeres) obtenidos del Departamento de Osteologia de los Museos Nacionales de Kenya se utilizaron para este estudio. Fueron identificados la presencia de puentes completos posteriores del atlas (canal retroarticular) y puentes laterales (foramen supratransverso). Se realizaron las mediciones de los diametros del foramen y los foramenes transversos ipsilaterales, y se calcularon sus areas. Puentes completos posteriores se observaron en el 14,6% y 13,6% de los lados derecho e izquierdo, respectivamente. El puente lateral se encontro en el 3,9% de los casos en el lado derecho solamente. Los puentes completos posteriores tuvieron un area transversal de 23,44mm2 en el lado derecho y 24,98mm2 en el lado izquierdo. Los puentes laterales tuvieron un area media de seccion transversal de 27,30mm2. En los lados derecho e izquierdo se encontrron foramenes transversos con un area promedio de seccion transversal de 36,30mm2 y 37,20mm2 respectivamente, lo que fue significativamente mayor que el de los puentes completos ipsilaterales y posteriores. Las dimensiones mas pequenas de los puentes atlas completos en comparacion con los foramenes transversos ipsilaterales sugieren que pueden predisponer a la insuficiencia vertebrobasilar, sindromes de Barre-Lieou y cervical debido a la compresion de los contenidos en los foramenes.

Course of the hepatic inferior vena cava in a Kenyan population.

The course of the hepatic inferior vena cava (HIVC) has a wide range of variations which are relevant in hepato‐vascular surgery and liver transplantation. Eighty livers were studied for hepatic course and axial orientation of the HIVC. The HIVC was found to run in an incomplete tunnel in 43.8% of the cases (n = 35), complete tunnel in 32.5% of the cases (n = 26) while in the rest, it was contained in a shallow groove on the retrohepatic surface. It assumed an oblique course in relation to the longitudinal axis of the liver in 60% of the cases (n = 48). The findings of this study vary to a wide range from those reported previously, and call for extra caution during surgical operations involving the HIVC region. Clin. Anat. 22:610–613, 2009.