Posterior Fontanelle Research Articles

Demonstration of cranial sutures and fontanelles at 15 to 16 weeks of gestation: a comparison between two‐dimensional and three‐dimensional ultrasonography

The purpose of this study was to evaluate the feasibility of obtaining good quality three-dimensional ultrasound pictures of the cranial sutures and fontanelles and to compare between two-dimensional and three-dimensional ultrasound in identifying the normal appearance of cranial sutures and fontanelles by the transvaginal approach at 15 to 16 weeks of gestation. Fifty fetuses were prospectively evaluated by two-dimensional and three-dimensional transvaginal sonography between 15 and 16 weeks of gestation. The sagittal, coronal, lambdoidal, and metopic sutures, as well as anterior and posterior fontanelles, were inspected. Three-dimensional ultrasound enabled visualization of all sutures in 37 (74%) fetuses compared to 28 (56%) fetuses examined by two-dimensional ultrasonography (p = NS). The visualization of the sagittal suture was significantly superior by three-dimensional ultrasonography compared to two-dimensional ultrasonography (50 (100%) vs 35 (70%), p < 0.001). No significant difference between the two modalities was found in visualization of the fontanelles. Sutures and fontanelles are usually satisfactorily demonstrated by two-dimensional and three-dimensional ultrasound at 15 to 16 weeks of gestation. The sagittal suture is difficult to visualize using two-dimensional ultrasound, and three-dimensional ultrasound appears to be the best method for its demonstration.

Index of Suspicion in the Nursery

At 39 weeks’ gestation, a male infant is born to a healthy 27-year-old, gravida 2, para 1 mother. The pregnancy was uncomplicated, with no significant prenatal history and negative group B Streptococcus screening results. The mother has no history of sexually transmitted disease, autoimmune disease, or hereditary mechanobullous disorders. Labor and delivery are uncomplicated. A fetal scalp monitor is not used. The newborn appears vigorous and has a lusty cry. He transitions without difficulty and is given an Apgar score of 9 at both 1 and 5 minutes (subtraction of 1 point for color each time). On physical examination, he appears well, with good color and tone. He weighs 3,580 g. He is breathing normally and has normal heart sounds. His anterior and posterior fontanelles are soft, open, and flat. His head is normocephalic and without evidence of trauma. With the exception of a 5-cm mongolian spot in the sacral region, his skin is clear. He is transferred to an open crib for routine newborn care. At approximately 30 hours of age, the nurse calls the pediatrician because of “blisters” noted on the patient’s scalp. The patient has been breastfeeding well and has both voided and stooled since delivery. He has maintained a stable temperature and normal vital signs. On physical examination, the infant appears well and is in no …

The role of three-dimensional ultrasound in visualizing the fetal cranial sutures and fontanels during the second half of pregnancy.

The aim of this study was to evaluate the significance of three-dimensional (3D) ultrasound in visualizing fetal cranial sutures and fontanels and to determine factors that could influence visualization and image quality. Serial 3D ultrasound examinations were evaluated for visibility of fetal cranial sutures and fontanels, image quality and possible influencing parameters in the second half of pregnancy. Thirty fetuses were scanned at four different gestational ages providing a data set of 120 cases. Most (82-100%) cranial sutures and fontanels could be visualized with 3D ultrasound. However, the sagittal suture and posterior fontanel were visualized in only 47% and 42%, respectively. Gestational age significantly influenced the visibility of the sutures and fontanels, image quality decreasing with advancing gestational age. 3D ultrasound can be a reliable technique for visualizing most fetal cranial sutures and fontanels. By performing a sagittal and a transverse scan, most of the sutures and fontanels can be made visible during the second half of pregnancy. Visualization depends on gestational age.

Trichomycterus maracaya, a new catfish from the upper rio Paraná, southeastern Brazil (Siluriformes: Trichomycteridae), with notes on the T. brasiliensis species-complex

Trichomycterus maracaya, a new species of Trichomycteridae, is described from a streamlet in the upper rio Paraná, Poços de Caldas, State of Minas Gerais, southeastern Brazil. The following putative autapomorphies distinguishes T. maracaya from congeneric species: 1) row of lateral blotches not forming a stripe at any phase during ontogeny; 2) superficial layer of pigmentation of juveniles and large (presumably adults) specimens consisting solely of scattered chromatophores. Furthermore, the new species is characterized by a combination of yellow ground color in life and mottled pattern formed by small to medium-sized, brown, irregularly-coalescent, well-defined deeper-lying blotches, and more superficial dots on the body. Trichomycterus maracaya is assigned to the T. brasiliensis species-complex (which includes T. brasiliensis, T. iheringi, T. mimonha, T. potschi, T. vermiculatus, and several undescribed species apparently endemic to the main river basins draining the Brazilian Shield) based on the presence of: 1) blotches in four longitudinal rows of deeper-lying pigmentation on the trunk large, horizontally-elongated, and well-defined; 2) pectoral fin with I+5-6 rays; 3) separation between the anterior and posterior cranial fontanels by the primordial epiphyseal cartilaginous bar being present only in larger specimens; and 4) pelvic-fin bases very close to each other, sometimes in contact.

The late Miocene Phractocephalus catfish (Siluriformes: Pimelodidae) from Urumaco, Venezuela: additional specimens and reinterpretation as a distinct species

Based on additional specimens the fossil pimelodid catfish from the upper Miocene Urumaco Formation, Falcón State, Venezuela originally assigned to the extant species Phractocephalus hemioliopterus is described as a new, extinct species. †Phractocephalus nassi n. sp. is diagnosed by the following combination of characters: 1) posterior half of frontals and anterior half of supraoccipital with elongate, coarse ridges and sulci in addition to reticulating ridges and subcircular pits; 2) very broad and ornamented mesethmoid bone; 3) lateral ethmoid margin convex and eliminating orbital notch but not projecting far anteriorly over palatine condyle; 4) anterior cranial fontanelle closed or represented by a small pit; 5) supraoccipital process rounded laterally and posterolaterally, concave posteriorly and completely concealing Weberian complex in dorsal view; 6) opercle covered with reticulating ridges and pits; 7) cleithrum coarsely ornamented along ventral edge and bulging outward lateral to spine articulation; 8) pectoral spine mostly ornamented with coarse ridges and sulci. †Phractocephalus nassi is compared to modern P. hemioliopterus and an undescribed extinct species from the upper Miocene Solimões Formation, Acre, Brazil. New diagnostic characters of Phractocephalus are presented that apply to the modern and fossil species, including: 1) ornamentation of skull, pectoral girdle and fin spines comprising a coarse meshwork of reticulating ridges surrounding rounded pits plus some elongate ridges and sulci; 2) supraoccipital posterior process greatly expanded laterally and posteriorly behind occipital wall; 3) lateral ethmoid and sphenotic broadly sutured behind eye; 4) anterior cranial fontanelle reduced or completely closed and posterior cranial fontanelle closed; 5) vomerine tooth plate large, roughly pentagonal to triangular in form, and with fine teeth. Today Phractocephalus ranges widely throughout the lowland Orinoco, Amazon and Essequibo basins. However, the genus does not occur west or north of the Andes or Venezuelan coastal ranges. Recognizing the Urumaco Phractocephalus as a distinct species does not alter the obvious conclusion that this catfish marks a large river connection between the Caribbean coastal region and the Orinoco system during at least part of the Neogene. Other Urumaco fossils show this same biogeographic relationship.

Mystus impluviatus: A New Species of Bagrid Catfish (Teleostei: Bagridae) from Eastern Borneo

Abstract A new species of bagrid catfish in the genus Mystus is described from the Mahakam River drainage in eastern Borneo. Mystus impluviatus closely resembles Mystus nigriceps and Mystus castaneus but differs in having a second posterior fontanel on the supraoccipital. It can be further distinguished from M. nigriceps and M. castaneus a combination of the following characters: maximum height of adipose fin 4.7–6.0% SL, length of adipose fin base 31.6–36.1% SL, long second and third dorsal fin rays, causing the dorsal fin to appear less rounded, maximum height of pectoral spine serrations 3.6–4.8% of spine length, a deeply forked caudal fin with a slender upper lobe, and a brown body with a distinct dark triangular patch on the base of the caudal peduncle.

Potential pitfalls in cranial sonography

We present several anatomic variants of the brain and artifacts related to scanning techniques which could be misinterpreted as lesions on neonatal cranial sonography. The findings were derived from US studies performed on 176 premature infants and 26 full-term newborns, using the anterior, posterior and mastoid fontanelles as acoustic windows. The pseudolesions are divided into three groups: ventricular system (asymmetric lateral ventricle size and coarctation of the lateral ventricles); choroid plexus ("split" choroid, "truncated" choroid and choroid cyst); and brain parenchyma (peritrigonal blush, thalamic pseudolesion, pseudo-absence of the inferior vermis, occipital pseudomass and calcar avis simulating intraventricular clot). We provide images of these pseudolesions and clues to their differentiation from true brain pathology. Images of several brain disorders are included for comparison. Knowledge of these potential pitfalls is essential for proper interpretation of US brain studies and will help to avoid the use of other more invasive diagnostic tests. Misleading images seen on US examination of the neonatal brain that could be misinterpreted as pathology are presented, with clues to their differentiation from true lesions.

A primitive chondrichthyan braincase from the Early Devonian of South Africa

ABSTRACT The earliest-known chondrichthyan braincase, from the Early Devonian (Emsian) Gydo Formation of South Africa, is described along with parts of the visceral skeleton. Only the ventral surface of the braincase is exposed, but CT-scanning permits the investigation of its unprepared regions and internal features. There is a persistent cranial fissure (as in osteichthyans) separating the trabecular and parachordal regions. The parachordal cartilage is identical to isolated endoskeletal elements referred to Pucapampella from the Middle Devonian of Bolivia. The semicircular canals are arranged as in osteichthyans and chimaeroids, with a crus commune connecting the anterior and posterior canals dorsally. The elongate palatoquadrate has an ethmoidal and palatobasal articulation (it is unknown if a postorbital articulation was present). The mandibular joint is positioned lateral to the widest part of the parachordal region, and the hyoid arch probably helped support the jaw. The South African specimen demonstrates unequivocally that some features previously known only in osteichthyans (e.g., ventral otic fissure, posterior dorsal fontanelle, palatobasal articulation) were also present in primitive chondrichthyans and are actually plesiomorphic hold-overs whose distribution was primitively more universal among gnathostomes. Fossils rarely overturn the phylogenetic status of morphological characters at such deep phylogenetic levels, perhaps because their wider original distribution pattern was short-lived and is rarely recovered from the fossil record.

A new view of the neonatal brain: clinical utility of supplemental neurologic US imaging windows.

Anterior fontanelle imaging has traditionally been the mainstay of neonatal cranial ultrasonography (US). However, this traditional approach has limited diagnostic accuracy, which has led to increasing use of two alternate neurologic US imaging techniques: posterior fontanelle imaging and mastoid fontanelle imaging. These alternate techniques can help detect pathologic conditions and structural malformations in the neonatal brain. Posterior fontanelle imaging allows improved detection of intraventricular hemorrhage. This technique better demonstrates subtle differences in echogenicity between clot and a choroid glomus and depicts clot extending into the occipital and temporal horns. Mastoid fontanelle imaging is particularly useful in detecting hemorrhage involving the brainstem, cerebellum, and subarachnoid cisterns. It greatly facilitates clot detection in the fourth ventricle and cisterna magna because the tissues surrounding these structures are normally echogenic. Mastoid fontanelle imaging can also help distinguish holoprosencephaly from aqueductal stenosis and identify small malformations of the posterior fossa. Color Doppler US may help identify normal variants such as calcar avis and lobular choroid plexus, and adjunct magnetic resonance imaging can help distinguish normal structures from a true Dandy-Walker variant. Use of posterior fontanelle imaging and mastoid fontanelle imaging can significantly augment the diagnostic power of neurologic US.

Cranial Ultrasonography

Cranial Ultrasonography

Newborn screening for congenital hypothyroidism, Victoria, Australia, 1977-1997. Part 1: The screening programme, demography, baseline perinatal data and diagnostic classification.

Clinical, demographic and laboratory data from infants with congenital hypothyroidism (CH) born in the Australian state of Victoria from the commencement of neonatal screening in mid-1977 until December 1988 are reported. These provide a baseline for a 12-year prospective longitudinal study on physical and neuro-psychological outcome until mid-1997, the subject of a second paper. Infants with CH were detected using a primary TT4 screening test. Demographic data were collected prospectively using a clinical assessment protocol. Nearly all affected infants underwent 99mTc pertechnetate scanning at the initial assessment to determine the underlying aetiology of their hypothyroidism. 704,723 infants were screened and 199 with permanent primary hypothyroidism (one in 3,541) were identified. The most common aetiologies were thyroid ectopia (46%), thyroid aplasia (33%), and 'dyshormonogenesis' (11%). The clinical abnormalities classically described in CH were more evident in infants with aplasia, and the striking female preponderance in infants with thyroid dysplasia (syn. dysgenesis) was confirmed. Other features included increased frequencies of 'dyshormonogenesis' in infants of parents of Middle-Eastern origin and of labour induction in infants with dysplasia. A closed posterior fontanelle was not found in any infant with thyroid aplasia.

Three-dimensional transvaginal neurosonography of the fetal brain: 'navigating' in the volume scan.

Fetal neuroscan by ultrasound has gained in importance over recent years. Two-dimensional (2D) transvaginal sonography was an important step in understanding the constantly changing and developing fetal brain. The objective of this article is to describe the use of three-dimensional ultrasound of the fetal brain enhanced by the transvaginal transfontanelle scanning technique. Thirty-four pregnant patients were referred to us because of a history of brain anomaly or suspected brain pathology. The fetuses were scanned transvaginally. Two-dimensional as well as three-dimensional (3D) images were generated. The volumes obtained by the 3D-ultrasound machine were displayed in the three conventional orthogonal planes (coronal, sagittal and axial). Of the 34 fetuses 10 had normal brain anatomy and 24 had brain pathology. In all 34 cases the 2D images as well as the 3D volumes were of diagnostic quality and all three planes could be obtained. The axial sections could only be obtained by the 3D re-construction of the volume scans. The 2D images produced were acquired from a common point originating from the foot print of the transvaginal probe at the fetal anterior fontanelle or the sagittal suture, the sections 'radiate' from this point. Therefore, these sections are not parallel sections, but are oblique to each other. In contrast, the 3D volume could be examined using the classical parallel sections in all three orthogonal planes. The posterior fossa could be seen better if the footprint of the probe was placed over the posterior fontanelle or on the sagittal suture. The marker dot enabled a precise creation of anatomy and pathology. In the 'angio mode' it was possible to follow the anterior cerebral and pericallosal artery. The 3D-ultrasound technology using the transvaginal approach is effective and practical to perform during fetal neuroscan. The ability to 'navigate' in the volume and the 'marker dot' enables exact location of normal structures and evaluation fetal brain pathology. The volume can be reviewed over and over again, can be mailed to an expert, could be shown to consultants (pediatric neurology and neurosurgeons) and used for teaching.

Fontanelle and uncinate process in the lateral wall of the human nasal cavity.

Although a complete anatomic knowledge of the fontanelle is a prerequisite to perform a surgical antrostomy opening, little is known about the boundary, shape, and size of the fontanelle. The purpose of this paper is to determine the best site for maintaining the patency of a surgical antrostomy opening by defining the anatomic boundaries, shape, and size of the fontanelle as well as its histological structure. One hundred sagittally divided heads were utilized. Mucosa overlying the lateral nasal wall was carefully removed with an operating microscope under 6x magnification. In some cases, a double mucous membrane, including the posteroinferior portion of the uncinate process, was cut as a whole and embedded in paraffin. The sections were stained with H&E. The boundary of the fontanelle and the location of the natural ostium were described in detail. Eight patterns of the posteroinferior portion of the uncinate process were observed. There were three major fontanelle shapes when observed from the medial aspect to the lateral: triangular, pencil-like, and oval. The triangular type was the most common. The anterior portion of the fontanelle was shorter than the posterior when observed medially and was wider than the posterior portion when observed inferiorly. The anterior portion of the fontanelle is more prone to stenosis than the posterior portion. An antrostomy in the posterior fontanelle may be more ideal for a middle meatal antrostomy of the maxillary sinus.

Cerebellar vermis diameter at cranial sonography for assessing gestational age in low-birth-weight infants.

Clinical assessment of gestational age for very-low-birth-weight infants is often inaccurate. Survival rates are more dependent on gestational age than on the birth weight. To assess whether cerebellar vermis diameter might predict gestational age in infants under 2,000 g and/or under 32 weeks' gestation. We carried out a retrospective review of the hard-copy images of midline sagittal views of the cerebellum obtained at cranial sonography, performed via the anterior or posterior fontanelle, in 518 infants admitted to a regional neonatal intensive care unit between June 1991 and November 1996. The vermis diameter was measured from the base of the fourth ventricle to the junction of folium and tuber vermis. We generated regression equations for estimating gestational age from vermis diameter, and from vermis diameter and birth weight, for the 86 infants of known gestational age (less than 32 weeks), with birth weight under 2,000 g and who had scans carried out within 1 week of birth. Measurement of cerebellar vermis diameter alone allowed prediction of gestational age to +/- 1.53 weeks using a 68 % prediction interval, or +/- 3.0 weeks using a 95 % prediction interval. Gender was not significant in the regression analysis. Cerebellar vermis diameter predicts gestational age with slightly more precision than the new Ballard score.

Hyperechoic foci in the thalamic region imaged via the posterior fontanelle: a potential mimic of thalamic pathology.

We have incidentally noted foci of increased thalamic echogenicity (FITE) on cranial sonographic images obtained via the posterior fontanelle (PF) that were not confirmed on images obtained while scanning through the anterior fontanelle (AF). Therefore, we postulated that this is a normal variant of PF imaging rather than true thalamic pathology. The purpose of this study was to determine the incidence of FITE detected on posterior and anterior fontanelle images. Parasagittal images were obtained bilaterally through the trigone of the lateral ventricles (including the thalami) via both the anterior and posterior fontanelles in 15 consecutive neonates (30 thalami) and evaluated independently by two pediatric radiologists for the presence or absence of FITE. Thalami were graded as grade 0 (no FITE), grade 1 (possible FITE), or grade 2 (definite FITE). Follow-up CT (n = 3) and MR (n = 1) were reviewed. FITE were absent in 87 % of thalami imaged via the AF, and possible FITE were present in 13 % of these cases. No cases of definite FITE were identified via the AF. However, possible FITE were identified in 33-40 % of thalami and definite FITE were seen in 33 % of thalami imaged via the PF. FITE seen only on images obtained through the PF on cranial sonography are a normal finding and should not be attributed to thalamic hemorrhage or ischemia.

Variation in fontanelle size with gestational age.

There is scanty data in the literature on the variation of fontanelle size with gestational age. This relationship was studied in 250 neonates delivered at gestational ages of 29-41 weeks at the University College Hospital, Ibadan, Nigeria. Anterior fontanelle size showed a low positive correlation with gestational age (r = 0.15). However, controlling for occipitofrontal circumference reduced this correlation to 0.12. Mean anterior fontanelle size increased with increasing gestational age but the anterior fontanelle size: occipitofrontal circumference ratio remained remarkably constant over the range of gestational age studied. The posterior fontanelle size did not show a significant correlation with gestational age and the prevalence of closed posterior fontanelles at birth did not differ significantly between term and preterm neonates. It is concluded that anterior fontanelle size does show a low positive correlation with gestational age but maintains the same ratio with head circumference at least during the third trimester of intrauterine life. Posterior fontanelle size shows no linear relationship with gestational age.

A Poem For Obstetricians

Dr Aldo Vacca, Director of Obstetrics, Redcliffe and Caboolture Hospitals, Queensland has made the vacuum extractor his major clinical interest if not his life's passion. He has taught hundreds of residents, registrars and consultants the principles and technique of the safe use of this instrument and has spoken at meetings all over the world about the science and art of vacuum extraction. He has published one of the few well conducted randomized controlled trials of vacuum extraction (1), and he is rightly considered a world authority on the topic. One of the main points he is stressing in the passing on of his experience in the safe use of the instrument is correct positioning of the cup over the posterior fontanelle which led some years ago to his registrar suggesting that a fitting epitaph for Aldo would be it's always more posterior than you think; in other words one needs to place the cup more posteriorly than you think — towards the occiput, regardless of the position of the head in the maternal pelvis. Aldo has provided the following poem, somewhat after the style of Banjo Patterson, which in a humorous way reiterates the important clinical point that he makes in his clinical teaching. This submission was arranged by Dr James F King with the approval of Dr Aldo Vacca.

Endonasal coagulation of the sphenopalatine artery in severe posterior epistaxis

Until a few years ago the surgical method of choice in treating uncontrollable nosebleeds from the posterior part of the nose was the transantral ligation of the maxillary artery as described by Seiffert (Caldwell-Luc approach). We introduce a surgical method to expose and coagulate the sphenopalatine artery through an endonasal approach. The middle meatus of the nose is exposed with a self supporting nasal speculum under the microscope (focus: 300 mm) and the maxillary sinus is opened through the posterior fontanelle. The medial wall of the maxillary sinus is removed from this opening to its end. Three to five millimeters posterior to this site, the foramen sphenopalatinum is exposed. The osseous lateral margin of the foramen is resected with the drill and the fossa pterygopalatina is thereby opened from the nose. The sphenopalatine artery can be exposed all the way to its origin from the maxillary artery and then coagulated. Thirty-one patients with severe epistaxis have been operated by this method since October 1993. No postoperative complications were observed in any cases. Thirty patients have had no further nosebleed since than (average follow-up 22.9 months). In one case of a patient with renal insufficiency a nose bleed occurred 15 day postoperatively following dialysis. It was controlled by ligation of the anterior ethmoid artery and of the peripheral branches of the external carotid artery. The endonasal coagulation of the sphenopalatine artery is the safest method to control bleeding from the posterior parts of the nose. It can be performed by anyone who is familiar with endonasal surgery. The disadvantages of the transanteral ligation of the maxillary artery as described by Seiffert (Caldwell-Luc approach, ligation not sufficiently peripheral) are avoided. The only competing method would be the embolization of the sphenopalatine artery which can not be applied in every hospital and which has a higher complication and failure rate. Since October 1993 when this method was introduced no additional bellocq tamponade was required in epistaxis.

Suture formation, premature sutural fusion, and suture default zones in Apert syndrome.

On the basis of our studies, we postulate that suture formation in Apert syndrome is related to the relative maturity of abutting calvarial bones. The fused coronal suture, a consistent manifestation at birth, develops first because the ossification centers of the frontal and parietal bones are in intimate contact early during intrauterine life. Calvarial immaturity and the megalencephalic brain characteristic of the Apert syndrome appear to work in concert to produce a widely patent midline calvarial defect extending from the glabella to the posterior fontanelle. Because sagittal growth in the coronal sutures cannot take place, the megalencephalic brain grows upward and laterally, and bulges forward through the midline defect. The defect fills in by coalescence of bony islands without proper suture formation because the gap to be bridged is so great that the time window for developing sutural interdigitations may have closed. Other sutures, such as the lambdoid, squamosal, and sphenotemporal, develop with normal interdigitations because abutting bone margins are in close enough proximity to permit suture formation.

Cerebellar vermis measurement at cranial sonography for assessing gestational age in the newborn weighing less than 2000 grams.

Prognosis of the very low birth weight infant depends more on gestational age than birth weight, but clinical assessment of gestational age of very low birth weight infants is inaccurate. We wished to determine how well cerebellar vermis dimensions might predict gestational age in infants of birth weight less than 2000 g. We obtained suitable midline sagittal images of the cerebellar vermis at cranial sonography, performed via the anterior or posterior fontanelle, in 41 infants, from the regional neonatal intensive care unit whose gestational age was known. We measured the cerebellar vermis area and diameter on the hard-copy image provided the margins of the vermis were clearly visible, the cerebellar tonsils were excluded from the image, and the anterior and posterior divisions of the corpus medullare were visible on the image. Vermis diameter was measured from the base of the fourth ventricle to the junction of folium and tuber vermis. Vermis area was calculated using a stereological method using a test system of regularly spaced points randomly placed over a magnified image of the cerebellar vermis. We generated regression equations for estimating gestational age using combinations of birth weight, vermis area, or vermis diameter for the 26 infants with birth weight of less than 2000 g for whom the cerebellar vermis measurements were obtained within one week of birth. Vermis area and diameter correlated very highly. They both can be used for predicting gestational age. The addition of either vermis area or diameter to birth weight improves accuracy of gestational age assessment. If birth weight was presumed to be unknown, cerebellar vermis area or diameter allow prediction of gestational age to within +/- 1.3 weeks (1 standard error) or +/- 2.5 weeks, using a 95% prediction interval. If the same method of reporting is applied to the New Ballard Score, the New Ballard Score predicts gestational age +/- 1.7 weeks (1 standard error) or +/- 3.4 weeks, using a 95% prediction interval.