Fontanelle Health Dictionary

Aspiration means the withdrawal of ?uid or gases from the natural cavities of the body or from cavities produced by disease. It may be performed for curative purposes; alternatively, a small amount of ?uid may be drawn o? for diagnosis of its nature or origin. An instrument called an aspirator is used to remove blood and ?uid from a surgical-operation site – for example, the abdomen or the mouth (in dentistry).

PLEURISY with e?usion is a condition requiring aspiration, and a litre or more of ?uid may be drawn o? by an aspirator or a large syringe and needle. Chronic abscesses and tuberculous joints may call for its use, the operation being done with a small syringe and hollow needle. PERICARDITIS with e?usion is another condition in which aspiration is sometimes performed. The spinal canal is aspirated by the operation of LUMBAR PUNCTURE. In children the ventricles of the brain are sometimes similarly relieved from excess of ?uid by piercing the fontanelle (soft spot) on the infant’s head. (See HYDROCEPHALUS.)... aspiration

An abnormal accumulation of CEREBROSPINAL FLUID, or CSF, within the skull, as a result of one or more of three main causes: (i) excessive CSF production; (ii) defective CSF absorption;

(iii) blockage of the circulation of CSF. Such disturbances in the circulation of the ?uid may be due to congenital reasons (most commonly associated with SPINA BIFIDA), to MENINGITIS, or to a tumour.

Symptoms In children, the chief symptoms observed are the gradual increase in size of the upper part of the head, out of all proportion to the face or the rest of the body. The head is globular, with a wide anterior FONTANELLE and separation of the bones at the sutures. The veins in the scalp are prominent, and there is a ‘crackpot’ note on percussion. The normal infant’s head should not grow more than 2·5 cm (1 inch) in each of the ?rst two months of life, and much more slowly subsequently; growth beyond this rate should arouse suspicions of hydrocephalus, so medical professionals caring for infants use centile charts for this purpose.

The cerebral ventricles are widely distended, and the convolutions of the brain ?attened, while occasionally the ?uid escapes into the cavity of the cranium, which it ?lls, pressing down the brain to the base of the skull. As a consequence of such changes, the functions of the brain are interfered with, and in general the mental condition of the patient is impaired. Untreated, the child is dull and listless, irritable and sometimes suffers from severe mental subnormality. The special senses become affected as the disease advances, especially vision, and sight is often lost, as is also hearing. Towards the end, paralysis is apt to occur.

Treatment Numerous ingenious operations have been devised for the treatment of hydrocephalus. The most satisfactory of these utilise unidirectional valves and shunts (tubes), whereby the cerebrospinal ?uid is bypassed from the brain into the right atrium of the heart or the peritoneal cavity. The shunt may have to be left in position inde?nitely.... hydrocephalus

This is the collection of 22 ?at and irregularly shaped bones which protect the brain and form the face (see BONE).

Arrangement of the bones In childhood, the bones are independent, gradually fusing together by sutures, and in old age fusing completely so that the cranium forms a solid bony case. At the time of birth the growth of several bones of the infant’s head has not been quite completed, so that six soft spots, or fontanellas, present; here the brain is covered only by skin and membranes, and the pulsations of its blood vessels may be seen. One of these spots, the anterior fontanelle, does not close completely until the child is 18 months to 2••• years old.

Parts of the skull The cranium, enclosing the brain, consists of eight bones, while the face, which forms a bony framework for the eyes, nose and mouth, consists of 14 bones. These two parts can be detached.

Shape of the skull The development of large central hemispheres of the brain in humans has in?uenced the skull shape. Unlike in other mammals, the cranium extends above as well as behind the face which therefore looks forwards. The skull’s proportions change with age: the cranium in children is larger in comparison with the face – one-eighth of the whole head – than is the case in adults, where sizes are about the same. Old age reduces the size of the face because of the loss of teeth and absorption of their bony sockets. Women’s skulls tend to be lighter and smoother with less obvious protuberances than those in men.... skull

n. the point on the top of the skull at which the coronal and sagittal *sutures meet. In a young infant this is an opening, the anterior *fontanelle.... bregma

n. premature closing of the *sutures and fontanelles between the cranial bones during development, resulting in the skull remaining abnormally small. Compare craniosynostosis.... craniostenosis

(osteogenesis) n. the formation of *bone, which takes place in three stages by the action of special cells (osteoblasts). A meshwork of collagen fibres is deposited in connective tissue, followed by the production of a cementing polysaccharide. Finally the cement is impregnated with minute crystals of calcium salts. The osteoblasts become enclosed within the matrix as osteocytes (bone cells). In intracartilaginous (or endochondral) ossification the bone replaces cartilage. This process starts to occur soon after the end of the second month of embryonic life. Intramembranous ossification is the formation of a *membrane bone (e.g. a bone of the skull). This starts in the early embryo and is not complete at birth (see fontanelle).... ossification