Status Marmoratus

Fig. 4.5. A-D. Patterns of sulcus configuration for gyral development score 2 (A or B), score 3 (C), and score 4 (D). From Van der Knaap et al. (1996), with permission ent brain areas using a five-point scoring system (Fig. 4.5): (1) The surface is smooth without gyri and sulci or there is, at most, some undulation of the cortical surface area. (2) Width of the gyri is greater than the depth of the sulci. (3) Width of the gyri is equal to the depth of the sulci. (4) Width of the gyri is less than the depth of the sulci. (5) Gyri and sulci are branched. Seven cortical areas were studied separately: (1) the frontal lobe minus the area of the central sulcus, (2) the area of the central sulcus, (3) the parietal lobe minus the area of the central sulcus, (4) the occipital lobe minus the medial area, (5) the medial occipital area, (6) the posterior part of the temporal lobe, and (7) the anterior part of the temporal lobe. The five stages of gyration distinguished are shown in Figs. 4.6-4.10. The ages of the children ranged from 30 to 42 weeks. At all ages the development of the rolandic area and the medial part of the occipital lobe (areas 2 and 5) was most advanced. In the parietal area, occipital area and posterior temporal area (areas 3,4, and 6), an intermediate rate of gyral development was found. Gyral development was slowest and latest in the frontal and anterior temporal areas (areas 1 and 7).

Gyral Development

Fig.4.6. Sagittal Trweighted, and coronal and transverse bordering gyrus.The frontal and temporal cortical surface is

T2-weighted images in a preterm infant at a GA of 30 weeks, smooth;the cortex is slightly undulating in the posterior area.

showing stage 1 gyration. The depth of the central, parieto- From Van der Knaap et al. (1996), with permission occipital and calcarine sulci is about equal to the width of the

Fig.4.6. Sagittal Trweighted, and coronal and transverse bordering gyrus.The frontal and temporal cortical surface is

T2-weighted images in a preterm infant at a GA of 30 weeks, smooth;the cortex is slightly undulating in the posterior area.

showing stage 1 gyration. The depth of the central, parieto- From Van der Knaap et al. (1996), with permission occipital and calcarine sulci is about equal to the width of the

Status Marmoratus
Fig. 4.7. Preterm infant at a GA of 32 weeks. Sagittal Tr and coronal and transverse T2-weighted images show gyration stage 2. The central and calcarine sulci are now deeper than

the bordering gyri. Compared with stage 1 sulci are better defined and increased in number in the remaining areas.From Van der Knaap et al.(1996), with permission

Van Der Knaap Pattern Myelination

Fig. 4.8. Gyration at a GA of 36 weeks. Sagittal and coronal defined and more numerous.The depth of the sulci is equal or

Tr and transverse T2-weighted images demonstrate stage 3 greater than the width of the gyri in most areas. From Van der gyration.The central sulcus and sulci of the medial occipital Knaap et al. (1996), with permission area are now becoming branched. Sulci are becoming better

Fig. 4.8. Gyration at a GA of 36 weeks. Sagittal and coronal defined and more numerous.The depth of the sulci is equal or

Tr and transverse T2-weighted images demonstrate stage 3 greater than the width of the gyri in most areas. From Van der gyration.The central sulcus and sulci of the medial occipital Knaap et al. (1996), with permission area are now becoming branched. Sulci are becoming better

Gyri And Sulci
Fig. 4.9. Gyration at a GA of 39 weeks. Sagittal and coronal Tr and transverse T2-weighted images depict stage 4 gyra-tion.The central and sulci of the medial occipital area are now branched.The number of sulci and gyri has increased again.

The sulci have a closed form in most areas. The depth of the majority of sulci is greater than that of the bordering gyri.From Van der Knaap et al.(1996), with permission

Delayed Myelination
Fig. 4.10. Gyration at a GA of 42 weeks,depicted on sagittal T1-weighted,and coronal and transverse T2-weighted images,show-ing stage 5 gyration. Branching of sulci is now seen in all areas. From Van der Knaap et al.(1996), with permission

4.7 Delayed Myelination, Irregular Myelination, Hypomyelination, and Arrest of Myelination

Once MRI criteria for normal progress of myelination have been established, it is possible to diagnose delays in this process. If it is true that myelination expresses functional maturity a correlation between delay in myelination and delayed development of psychomotor functions can be expected. Roughly speaking, this appears to be the case. We have been able to confirm it in a group of children with hydrocephalus, in whom MRI and neuropsychological data were obtained before and twice after shunting. There was a strong correlation between (a) the progress of myelination as compared with the normal myelination standard and (b) the progress of mental development as compared with the normal developmental standard. It is important to follow up the progress of myelination in any child in whom a delay is suspected, to see whether, and if so when, the child catches up with normal myelination. It might be assumed that a longer delay in the restoration of the normal pattern would coincide with a poorer prognosis.

There are many possible causes for a delay in myelination: hypoxia-ischemia, congenital infections, congenital malformations, chromosomal abnormalities, congenital heart failure, postnatal infections, hydrocephalus, hypothyroidism, hypercorti-solism,hypocortisolism, fetal intoxications, malnutrition, and inborn errors of metabolism. The delay is usually bilateral and symmetrical,but unilateral delay is seen in cases with hemimegalencephaly, unilateral porencephalic cysts, cerebral hemiatrophy, or unilateral periventricular leukomalacia.

The critical period in myelin development was initially thought to coincide with the proliferation of myelin-forming cells, rather than with the period of membrane accumulation. The mechanism of 'stunting' of oligodendroglial proliferation as a cause of hy-pomyelination has been under discussion, because in animal research no major deficits of oligodendro-cytes could ever be established, except in severely starved animals. Therefore the induction of myelin membrane formation, rather than cell proliferation, seems to be the actual critical event. Damage in critical periods is often limited to areas in which myelina-tion is beginning at that time. This knowledge is helpful in establishing the time of insult in infants and children.

Irregular myelination with local or generalized hypermyelination, or myelination not following the normal routes of progress, is rare, but is seen occasionally. Hypermyelination, or advanced myelination, has been observed in patients with Sturge-Weber syndrome. It has been suggested that epileptic seizures may stimulate myelination. However, advanced myelination or hypermyelination is not seen in most patients with infantile forms of epilepsy. Local hypermyelination in the basal ganglia is manifest histologically as the so-called status marmoratus, a late sequela of perinatal hypoxia. In this case the myelination does not involve the proper targets and does not occur around axons but around astrocytic extensions. Because of the low signal intensity of the basal ganglia on T2-weighted images and the dark appearance of myelin in this sequence, MRI has so far not succeeded in identifying this condition.

Hypomyelination or arrest of myelination occurs in Pelizaeus-Merzbacher disease, a disorder of proteo-lipid protein synthesis, one of the major myelin proteins. In this disorder no myelin, or only very little, is produced. In Salla disease, a lysosomal storage disorder, and DNA repair disorders such as Cockayne syndrome and trichothiodystrophy with sun hypersensi-tivity hypomyelination is also present. To establish a secure diagnosis of retarded or arrested myelination, at least two observations sufficiently far apart are necessary.

4.8 Iconography of Myelination and Gyration

Illustrations in this chapter show the progress of gyration (Figs. 4.4-4.10) and myelination in normal neonates and infants (Figs. 4.11-4.23). Many examples of disturbances of myelination are found in the other chapters in this book. In Table 4.4 the myelina-tion of some important structures on MRI is indicated. In some cases a more detailed look at structures in relation to their surroundings is useful,in order to see how contrast changes over time. The structures in the posterior fossa are a good example (Fig. 4.3). We also include an example of diffusion-weighted imaging in estimating the progress of myelination (Fig. 4.24).

Status Marmoratus

Fig. 4.11. Myelination at a GA of 32 weeks. The sagittal Tr weighted series (upperrow) shows the features of the premature brain nicely: lack of gyration in the frontal areas, with some gyration in the parietal and occipital lobes.The midsagit-tal image shows myelin present in the medulla oblongata,the

Fig. 4.11. Myelination at a GA of 32 weeks. The sagittal Tr weighted series (upperrow) shows the features of the premature brain nicely: lack of gyration in the frontal areas, with some gyration in the parietal and occipital lobes.The midsagit-tal image shows myelin present in the medulla oblongata,the dorsal part of the pons, the mesencephalon, and the corpus medullare of the cerebellum. The transverse T1-weighted series shows the same features and gives a good impression of the high water content of the unmyelinated white matter

Myelination And Unmyelination Infants

Fig. 4.12. Myelination at a GA of 39 weeks. A sagittal Tr losum is still thin and also unmyelinated. From the basal gan-weighted SE series is shown from right to left.In the brain stem, glia, myelinated white matter tracts can be followed towards the basis pontis is still not myelinated (arrow).The corpus cal- the post-rolandic gyrus (arrows)

Fig. 4.12. Myelination at a GA of 39 weeks. A sagittal Tr losum is still thin and also unmyelinated. From the basal gan-weighted SE series is shown from right to left.In the brain stem, glia, myelinated white matter tracts can be followed towards the basis pontis is still not myelinated (arrow).The corpus cal- the post-rolandic gyrus (arrows)

Basis Pontis

Fig. 4.13. Myelination 2weeks after birth at term,as seen on a T1-weighted transverse inversion recovery (IR) series. Myelination is seen in the medulla oblongata, middle cerebellar peduncle, tegmentum pontis (especially medial lemniscus, OTTOWs),colliculus inferior,decussation of the superior cerebel

Fig. 4.13. Myelination 2weeks after birth at term,as seen on a T1-weighted transverse inversion recovery (IR) series. Myelination is seen in the medulla oblongata, middle cerebellar peduncle, tegmentum pontis (especially medial lemniscus, OTTOWs),colliculus inferior,decussation of the superior cerebel lar peduncles, optic tracts, posterior limb of the internal capsule, white matter tracts in the basal ganglia and ascending tracts towards the post-rolandic gyrus. Note in the upper images that cortical gray matter is also myelinated

Status Marmoratus

Fig. 4.14. T2-weighted transverse series of myelination 2 weeks after birth at term for comparison.Cerebellar myelination is still in stage 1:the hilus of the dentate nucleus is bright; the dentate nucleus is surrounded by a dark band (arrow), again followed by bright cerebellar white matter. Contrast inversion of these structures during the progress of myelination

Fig. 4.14. T2-weighted transverse series of myelination 2 weeks after birth at term for comparison.Cerebellar myelination is still in stage 1:the hilus of the dentate nucleus is bright; the dentate nucleus is surrounded by a dark band (arrow), again followed by bright cerebellar white matter. Contrast inversion of these structures during the progress of myelination will give clues to the age of myelination. On T2-weighted images the tegmentum pontis (arrow) and mesencephalon are darker than the ventral pons. Myelin can also be seen in the superior vermis, posterior limb of the internal capsule, basal ganglia and ascending tracts into the post-rolandic gyrus (arrows)

Status Marmoratus Basal Ganglia

Fig. 4.15. In the posterior fossa T2-weighted images show that cerebellar myelination has progressed to stage 2 in this 2-month-old infant.The bright ring around the dentate nucleus has disappeared, but the peripheral white matter of the cerebellum is still bright.There is still a difference between the

Fig. 4.15. In the posterior fossa T2-weighted images show that cerebellar myelination has progressed to stage 2 in this 2-month-old infant.The bright ring around the dentate nucleus has disappeared, but the peripheral white matter of the cerebellum is still bright.There is still a difference between the basis pontis and tegmentum pontis, although much less pronounced than before. In the mesencephalon, the pyramidal tracts and decussation of the superior cerebellar peduncles can be identified

Pyramidal Tract Mesencephalon

Fig. 4.16. IR images at 3 months. The myelinated structures can easily be identified. Note the beginning of myelination in the pyramidal tracts in the mesencephalon (large white arrow) and the strongly myelinated decussation of the superior cerebellar peduncles (small black arrow). The colliculus inferior (blackarrow) and the auditory tracts are also clearly myelinat

Fig. 4.16. IR images at 3 months. The myelinated structures can easily be identified. Note the beginning of myelination in the pyramidal tracts in the mesencephalon (large white arrow) and the strongly myelinated decussation of the superior cerebellar peduncles (small black arrow). The colliculus inferior (blackarrow) and the auditory tracts are also clearly myelinat ed. The optic tract is myelinated, as is the optic radiation. The posterior limb of the internal capsule is fully myelinated at the postnatal age of 2 weeks. Myelin has now spread to the pre-central gyrus and will advance dorsally and ventrally to myelinate the occipital,the frontal and,finally,the temporal lobes

Corpus Mamillare Pet
Fig. 4.17. At the age of 5 months the genu of the corpus callosum starts to myelinate.On IR images myelination will soon appear to be complete.T2-weighted images will then be more useful in providing information about maturation of the brain
Corpus Callosum Maturation Month Child

Fig. 4.18. T2-weighted series at 4 months of age. In the pons, basis and tegmentum have a low signal;the medial lemniscus has an even lower signal (arrow), as do the middle cerebellar peduncles. The corpus medullare of the cerebellum is myelinated, but myelination is not yet extending towards the cortex. At the level of the mesencephalon, the decussation of the

Fig. 4.18. T2-weighted series at 4 months of age. In the pons, basis and tegmentum have a low signal;the medial lemniscus has an even lower signal (arrow), as do the middle cerebellar peduncles. The corpus medullare of the cerebellum is myelinated, but myelination is not yet extending towards the cortex. At the level of the mesencephalon, the decussation of the superior cerebellar peducles,the colliculus inferior (arrow),the pyramidal tracts,the corpus mamillare and the optic tract have a low signal.The posterior limb of the internal capsule is also dark (arrows). A difference is visible between the unmyelinated white matter in the frontal and temporal regions and the occipital and parietal region where myelination has started

White Matter Gliosis Frontal Lobes
Fig. 4.19. T2-weighted coronal images at the age of 4 months, showing the difference between still unmyelinated white matter in the frontal and temporal lobe and the more advanced myelination posteriorly
Coronal Plane Genu Corpus Collasum
Fig. 4.20. Myelination at 7-8 months of age. On the T2-weighted images the central parts are now myelinated,includ-ing the genu of the corpus callosum. The crossover between

gray and white matter in the occipital and parietal areas has started;there is little contrast between gray and white matter. In the frontal and temporal regions this is not yet the case

Myelination Mri Year Old
Fig. 4.21. Myelination at 12-13 months.The adult contrast is now emerging in all lobes except the temporal lobe, the latest to myelinate.The T2-weighted series shows that the spread of myelin into the arcuate fibers is still not complete
Status Marmoratus
Fig. 4.22. Adult pattern of myelination on T2-weighted images in a 5-year-old child.The temporal lobes now also show the adult gray-white matter contrast
Myelination Child

Fig. 4.24. Diffusion-weighted-imaging (DWI) and diffusion tensor imaging (DTI) allow further refinement and quantitation of the progress of myelination.These images depict single-shot EPI with single diffusion gradient in slice, read or phase direction at b=1000, showing anisotropy of myelinated fibers depending on the gradient direction in a baby boy 3 months of age

Imaging For Baby Boy

Fig. 4.24. Diffusion-weighted-imaging (DWI) and diffusion tensor imaging (DTI) allow further refinement and quantitation of the progress of myelination.These images depict single-shot EPI with single diffusion gradient in slice, read or phase direction at b=1000, showing anisotropy of myelinated fibers depending on the gradient direction in a baby boy 3 months of age

Diffusion Fetus
Fig. 4.25. Images demonstrating evolution of FA over time, measured with 12+1 diffusion gradient settings
Table 4.5. Myelination on MRI: chronological table (WM white matter). From:Yakovlev and Lecours (1967), with permission

Regions of CNS

Fetal age (weeks)

Pregnancy Diet Plan

Pregnancy Diet Plan

The first trimester is very important for the mother and the baby. For most women it is common to find out about their pregnancy after they have missed their menstrual cycle. Since, not all women note their menstrual cycle and dates of intercourse, it may cause slight confusion about the exact date of conception. That is why most women find out that they are pregnant only after one month of pregnancy.

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