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PubMed2003

A case of frontal network amnesia.

A 63 year old man developed an amnesic syndrome coupled with an array of "frontal lobe" signs after bilateral small subcortical infarcts. His amnesia was characterised by severe difficulty in voluntary recall of recently memorised verbal and non-verbal materials, while his recognition for the same materials was less affected. The symptoms remained unimproved at a follow up evaluation eight months after onset. Magnetic resonance imaging showed two small circumscribed lesions, one in the dorsomedial nucleus of the left thalamus and the other in a region of the right globus pallidus and anterior limb of the right internal capsule. The mammillothalamic tracts and anterior nuclei of the thalami were clearly spared bilaterally. The left dorsomedial nucleus lesion disrupted the thalamofrontal circuit, while the anterior limb lesion of the right internal capsule disconnected the same circuit by damaging part of the anterior thalamic radiation. Thus the amnesia in this patient may have been caused by disruption of the bilateral thalamofrontal circuits. This type of amnesic pathology should be separated from more conventional types of amnesia that are produced by disruption of the so called Papez circuit or the Delay-Brion memory system.

Amnesia↗
PubMed2000

Striatocapsular haemorrhage.

Haemorrhages in the striatocapsular area, or striatocapsular haemorrhages (SCHs), have been regarded as a single entity, although the area is composed of several functionally discrete structures that receive blood supply from different arteries. We analysed the morphological and clinical presentations of 215 cases of SCHs according to a new classification method we have designed on the basis of arterial territories. SCHs were divided into six types: (i) anterior type (Heubner's artery); (ii) middle type (medial lenticulostriate artery); (iii) posteromedial type (anterior choroidal artery); (iv) posterolateral type (posteromedial branches of lateral lenticulostriate artery); (v) lateral type (most lateral branches of lateral lenticulostriate artery); and (vi) massive type. The anterior type (11%) formed small caudate haematomas, always ruptured into the lateral ventricle, causing severe headache, and mild contralateral hemiparesis developed occasionally. The outcome was excellent. The middle type (7%) involved the globus pallidus and medial putamen, frequently causing contralateral hemiparesis and transient conjugate eye deviation to the lesion side. About 50% of the patients recovered to normal. The posteromedial type (4%) formed very small haematomas in the posterior limb of the internal capsule and presented with mild dysarthria, contralateral hemiparesis and sensory deficit, with excellent outcome in general. The posterolateral type (33%) affected the posterior half of the putamen and posterior limb of the internal capsule and presented with impaired consciousness and contralateral hemiparesis with either language dysfunction or contralateral neglect. The outcome was fair to poor but there were no deaths. The lateral type (21%) formed large elliptical haematomas between the putamen and insular cortex. Contralateral hemiparesis with language dysfunction or contralateral neglect developed frequently but resolved over several weeks. The clinical outcome was relatively excellent except when the haematoma size was very large. The massive type (24%) formed huge haematomas affecting the entire striatocapsular area. Marked sensorimotor deficits and impaired consciousness, ocular movement dysfunctions including the 'wrong-way' eyes were observed quite frequently. The outcome was very poor with a case fatality rate of 81%. The clinico-radiological presentations suggested its origin was the same as the posterolateral type.

Adult↗
PubMed2001

Abulia and cognitive impairment in two patients with capsular genu infarct.

BACKGROUND: An internal capsule genu infarct has been rarely reported to cause cognitive impairment and behavioral changes. This clinical picture can be explained on anatomical and functional basis because important subcortical-cortical pathways traverse the internal capsule genu. We report 2 previously non-demented patients who developed acute confusional state, abulia, and moderate cognitive decline after the occurrence of an infarct in the capsular genu. METHODS: Clinical, neuropsychological, and MRI evaluation at baseline and 12-month follow-up. RESULTS: Abulia and cognitive impairment were still present 1 year after stroke. In 1 patient there were associated multiple lacunar infarcts and leukoaraiosis. In the other an old small left frontal infarct was also present. In both moderate cortical atrophy co-existed. CONCLUSIONS: We hypothesize that co-existing lesions, possibly associated with a sub-clinical reduction of cognitive functions, facilitate the development of a persistent clinically evident mental deficit after the occurrence of an infarct in the capsular genu.

Aged↗
PubMed2001

Reanalysis of multislice (1)H MRSI in amyotrophic lateral sclerosis.

The goal of this work was to reexamine previously published (1) brain spectroscopy data of abnormal metabolite ratios in amyotrophic lateral sclerosis (ALS). Toward this goal, (1)H MR spectroscopic imaging data from 10 ALS and nine control subjects were reanalyzed using improved data analysis techniques, including automated curve fitting and tissue-volume correction. In the motor cortex of ALS, N-acetyl aspartate (NAA) was 23% (P = 0.004) lower than in controls, and in the posterior internal capsule of ALS choline compounds (Cho) were 20% (P = 0.02) higher. This demonstrates that the metabolite ratio changes in ALS were due to NAA loss in the motor cortex (as expected) and Cho increase in the posterior internal capsule (not expected). Magn Reson Med 45:513-516, 2001.

Adult↗
PubMed1989

Nerve growth factor receptor immunoreactive profiles in the normal, aged human basal forebrain: colocalization with cholinergic neurons.

A monoclonal antibody raised against the receptor for nerve growth factor (NGF) has been used to map the distribution of NGF receptor-containing profiles within the human basal forebrain of four male and three female elderly patients without neurologic or psychiatric illness. Immunohistochemically processed tissue reveals a continuum of NGF receptor-positive neurons located within the medial septum, vertical and horizontal limb nuclei of the diagonal band, and nucleus basalis. NGF receptor-containing neurons are also found within the bed nucleus of the stria terminalis, the anterior commissure, the internal capsule, and the internal and external medullary laminae of the globus pallidus. Virtually all (greater than 95%) NGF receptor-containing neurons colocalize with the specific cholinergic marker choline acetyltransferase (ChAT) or the nonspecific marker acetylcholinesterase (AChE). Conversely, a few cholinergic perikarya are found which are not NGF receptor positive (and vice versa). These findings demonstrate that human basal forebrain neurons on which NGF receptor immunoreactivity is detected are primarily cholinergic and analogous to the nonhuman primate Ch1-Ch4 subgroups of Mesulam et al. (J. Comp. Neurol., 214:170-197, '83). NGF receptor-containing fiber tracts are observed emanating from the medial septum and vertical limb nucleus of the diagonal band coursing medially within the fornix. Another fascicle originating mainly from the nucleus basalis and travelling within the external capsule enroute to the cortex is observed innervating all cortical layers. Comparison of NGF receptor- and ChAT-containing neurons reveals cholinergic perikarya within the striatal complex, whereas virtually no NGF receptor-containing neurons are found in these structures. An occasional displaced NGF receptor-containing neurons is seen in the ventrolateral portion of the putamen and the white matter underlying the nucleus accumbens. These data are discussed in terms of the relationship of NGF receptor- and ChAT-containing neurons within the basal forebrain and in terms of the possible functional significance of NGF in normal and diseased brain.

Acetylcholinesterase↗
PubMed2002

Diffusion-tensor MR imaging of gray and white matter development during normal human brain maturation.

BACKGROUND AND PURPOSE: Conventional MR imaging findings of human brain development are thought to result from decreasing water content, increasing macromolecular concentration, and myelination. We use diffusion-tensor MR imaging to test theoretical models that incorporate hypotheses regarding how these maturational processes influence water diffusion in developing gray and white matter. METHODS: Experimental data were derived from diffusion-tensor imaging of 167 participants, ages 31 gestational weeks to 11 postnatal years. An isotropic diffusion model was applied to the gray matter of the basal ganglia and thalamus. A model that assumes changes in the magnitude of diffusion while maintaining cylindrically symmetric anisotropy was applied to the white matter of the corpus callosum and internal capsule. Deviations of the diffusion tensor from the ideal model predictions, due to measurement noise, were estimated by using Monte Carlo simulations. RESULTS: Developing gray matter of the basal ganglia and developing white matter of the internal capsule and corpus callosum largely conformed to theory, with only small departures from model predictions in older children. However, data from the thalamus substantially diverged from predicted values, with progressively larger deviations from the model with increasing participant age. CONCLUSION: Changes in water diffusion during maturation of central gray and white matter structures can largely be explained by theoretical models incorporating simple assumptions regarding the influence of brain water content and myelination, although deviations from theory increase as the brain matures. Diffusion-tensor MR imaging is a powerful method for studying the process of brain development, with both scientific and clinical applications.

Basal Ganglia↗
PubMed1988

Magnetic resonance imaging in young adults with cerebral infarction due to moyamoya.

The number, size, and location of cerebral infarctions, and blood flow in the middle cerebral artery as seen on proton magnetic resonance imaging were assessed in six white adults with angiographically documented moyamoya. Findings were correlated with clinical presentation, computed tomography, and angiography. Large hemispheric infarctions were found in five hemispheres, predominantly in watershed regions. Subcortical infarctions (n = 56) were found in all hemispheres. They were predominantly located in the centrum semiovale, in the distal beds of supply of the penetrating branches of the anterior and middle cerebral arteries. Infarction of the putamen was found in three hemispheres, caudate nucleus in four, globus pallidus in two, and anterior limb of the internal capsule in two. There were none in the posterior limb of the internal capsule, thalamus, brain stem, or cerebellum. Middle cerebral artery flow was visualized as a signal-void flow sign in only three hemispheres. Cerebral infarctions due to moyamoya are bilateral, multiple, often small, and asymptomatic, affecting predominantly the carotid circulation in watershed regions. Subcortical infarctions in the centrum semiovale and large hemispheric infarctions in hemodynamically compromised areas are the predominant findings.

Adolescent↗
PubMed1997

Identification of transient microglial cell colonies in the forebrain white matter of developing rats.

Herein, we describe the existence of distinct colonies of transient microglial cells that reside in well-defined zones of the forebrain white matter. Rats, aged at postnatal day (P) 0, P2, P5, P7, P10, P15 or adult, were anaesthetised with halothane gas, and various neural centres were injected unilaterally with the tracer biotinylated Dextran. The neural centres injected were cingulate or sensorimotor cortices, ventral nuclei of the dorsal thalamus, and the pontine reticular formation of the brainstem. Rats were allowed to survive to various stages, from 4 hours to 21 days, after the injection. They were then anaesthetised with sodium pentobarbitone, and their brains were aldehyde-fixed and processed by using standard methods. The following is a description of what is seen after injections at P0, P2, P5, P7, P10; we saw no labelled cells (described below) in the rats injected at P15 or adult. From 2 to 21 days after an injection of dextran into the above-mentioned centres, labelled microglial cell colonies, identified by using double-labelling with anti-OX-6 or Griffonia simplicifolia (Bandeiraea; isolectin B4), were seen in small isolated zones in the forebrain white matter. These colonies were in the corpus callosum, the dorsal and ventral regions of the external capsule, and the internal capsule. A striking feature of these labelled microglial cell colonies was that they were seen on both sides of the brain. Thus, regardless of the location of the injection site in either the cortex, thalamus, or brainstem, the same microglial cell colonies were labelled with dextran in the forebrain white matter. After injections of different coloured fluorescent dextrans into the cortex and into the brainstem of the same animal, many double-labelled cells in each of the colonies were seen. From our short-term survival cases (4 hours to 1 day), a rather strict sequence or progression of labelling of the colonies across the white matter from the injection site was seen; in general, the microglial cell colonies closest to the injection site became labelled well before (about a day) those further away. These results lead us to suggest that the microglial cells in each colony become labelled after a slow diffusion of the tracer through the extracellular space from the injection site.

Aging↗
PubMed2000

Cortical projections from the suprasylvian gyrus to the reticular thalamic nucleus in the cat.

The cat's suprasylvian gyrus was injected iontophoretically with either 4% wheat germ agglutinin-horseradish peroxidase, 4% dextran-fluororuby or 4% dextran-biotin. The locations of labelled fibres, presumed terminals and cell bodies were determined with the aid of a camera lucida attachment and computer aided stereometry. Cells from the crown of the suprasylvian gyrus project to the dorsal-most portion of the rostral half of the reticular nucleus. The region or 'sector' is distinct, albeit with some overlap, from the visual sector of the reticular nucleus defined by projections from adjacent extrastriate visual cortices. The projection from the suprasylvian gyrus to the reticular nucleus has a rough topography such that the caudal areas project to the more caudal aspects of the sector and rostral areas project to the more rostral areas of the reticular nucleus. There is a large degree of overlap of rostrocaudal projections from the suprasylvian gyrus within the sector, however, the projections originating from rostral sites are situated in a more ventral location compared to the projection originating from the caudal suprasylvian gyrus. Analysis of the distribution of biotin labelled presumptive terminals did not support the notion of 'slabs' or regional variation in terminal density across the mediolateral thickness of the reticular nucleus. In addition, a number of presumptive terminals were found within the internal capsule which coincided with the position of retrogradely labelled cells in the internal capsule following thalamic injections and appears to be part of the perireticular nucleus. The results suggest that the reticular nucleus may be segregated into sectors connected with modality specific cortical areas (e.g. striate and extrastriate visual areas) and nonspecific sectors connected with polymodal (e.g. area 7) cortical regions. The reticular nucleus and its connections with the suprasylvian gyrus may form an important link in binding eye movements to sensory integrative process through visuomotor and auditory thalamic connections.

Animals↗
PubMed1999

Reproducibility and accuracy of MR imaging of the brain after severe birth asphyxia.

BACKGROUND AND PURPOSE: MR imaging of the brain can be used to detect cerebral damage after suspected hypoxic-ischemic injury. This study examines the reproducibility and accuracy of MR imaging soon after severe birth asphyxia. METHODS: During a 48-month period, full-term newborn neonates, who died within the first week as a result of severe hypoxic ischemic encephalopathy, were included in the study if they had undergone early (<5 days old) MR imaging and postmortem neuropathologic studies. Two trained observers assessed reproducibility by examining multiple brain regions independently with current criteria and then defining and applying improved criteria. Accuracy of MR findings was tested by comparing the brain regions about which the two imaging raters agreed to those regions about which the two pathologists agreed. RESULTS: Eight neonates, with a median gestational age of 40 weeks (range, 38-40 weeks) and who suffered severe birth asphyxia, were included in the study. In the reproducibility study, MR imaging agreement was moderate when current criteria were used (k = .44). Using the improved criteria, agreement increased considerably (k = .62). Much of this improvement was due to limiting the analyses to the posterior limb of the internal capsule, thalamus, parietal cortex, hippocampus, and medulla. The posterior limb of the internal capsule was the most reliable region analyzed. MR imaging agreement was similar to that achieved by two experienced pathologists reviewing the histologic sections (k = .66). In the accuracy study, MR imaging abnormality was predictive of pathologic abnormality with a sensitivity of .79 and a positive predictive value of 1.0. The predictive value of a single MR imaging abnormality was .79 (95% confidence interval, .61-.96). CONCLUSION: Criteria that provide substantial reproducibility and accuracy for the interpretation of MR imaging findings very early after birth asphyxia can be derived.

Asphyxia Neonatorum↗
PubMedDate not supplied

Patterns of edema in tumors vs. infarcts: visualization of white matter pathways.

The computed tomographic (CT) scans of 339 patients with recent nonhemorrhagic cerebral infarct and 155 patients with supratentorial tumors were reviewed to evaluate the appearance of cerebral edema. White matter pathway edema characterized the CT pattern in 106 (68%) of the 155 tumor cases. In these 106 cases, there were 143 tumors, with edema in the arcuate white matter (73%), the external capsule (33%), the internal capsule (12%) and the corpus callosum (14%). In contrast, only four of the 339 cases of infarct had edema in the white matter pathways. In addition, 260 (77%) of the infarct cases had edema in both gray and white matter and 98% had at least gray matter involvement, while only two of the tumor cases had any gray matter edema. White matter pathway involvement with respect to tumor site is useful in differentiating tumor and infarct edema.

Brain Neoplasms↗
PubMed2001

Magnetic resonance imaging correlates of depression after ischemic stroke.

BACKGROUND: Depression affects up to 40% of patients with ischemic stroke. The relationship between site and size of brain infarcts and poststroke depression is still not well characterized. Further possible contribution and interaction of white matter lesions and brain atrophy has not been studied previously. We conducted a magnetic resonance image-based study of the radiologic correlates of depression in a large, well-defined series of patients with ischemic stroke. METHODS: Modified DSM-III-R and DSM-IV criteria were used to diagnose depressive disorders during a comprehensive psychiatric evaluation in 275 of 486 consecutive patients aged 55 to 85 years 3 to 4 months after ischemic stroke. A standardized magnetic resonance imaging protocol detailed side, site, type, and extent of brain infarcts and extent of white matter lesions and brain atrophy. RESULTS: Depressive disorders were diagnosed in 109 patients (40%). Patients with depression had a higher number and larger volume of infarcts affecting the prefrontosubcortical circuits, especially the caudate, pallidum, and genu of internal capsule, with left-sided predominance. Extent of white matter lesions and atrophy did not differ in patients with and without depression. Independent correlates of poststroke depression in a logistic regression model were mean frequency of infarcts in the genu of internal capsule on the left side (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.0-10.1), mean frequency of infarcts in the pallidum of any side (OR, 1.6; 95% CI, 1.1-2.3), and mean volume of infarcts in the right occipital lobe (OR, 0.98; 95% CI, 0.96-0.99). CONCLUSION: Lesions affecting the prefrontosubcortical circuits, especially on the left side, are correlates of depression after ischemic stroke.

Aged↗
PubMed2006

Brain developmental abnormalities in Prader-Willi syndrome detected by diffusion tensor imaging.

OBJECTIVE: The purpose of this work was to detect brain developmental abnormalities in Prader-Willi syndrome by using diffusion tensor imaging based on a high-field MRI system. METHODS: Eight patients with Prader-Willi syndrome and 8 age- and gender-matched normal control subjects were examined using a high-field (3.0 T) MRI system. Trace value and fractional anisotropy were assessed simultaneously in multiple representative brain regions: the deep gray matter (putamen, caudate head, and dorsomedial thalamus) and the white matter structures (frontal and parietal white matter, posterior limb of internal capsule, and corpus callosum). RESULTS: In Prader-Willi syndrome patients, trace value was found to be significantly higher in the left frontal white matter and the left dorsomedial thalamus, whereas fractional anisotropy was significantly reduced in the posterior limb of the internal capsule bilaterally, the right frontal white matter, and the splenium of the corpus callosum. The observed diffusivity characteristics indicate developmental abnormalities in these areas, which are highly consistent with the clinical features of Prader-Willi syndrome. CONCLUSIONS: The study provides the first objective evidence that Prader-Willi syndrome patients indeed have developmental abnormalities in specific areas of the brain, providing a new window toward understanding the pathophysiology of Prader-Willi syndrome.

Adolescent↗
PubMed2003

Treatment of patients with intractable obsessive-compulsive disorder with anterior capsular stimulation. Case report.

Obsessive-compulsive disorder (OCD) is a common, chronic, disabling anxiety disorder characterized by recurrent obsessive thoughts and uncontrolled repetitive acts. Although many patients respond to various pharmacological treatments, there is a cohort of patients with intractable or refractory disease. The authors present the case of a patient with intractable OCD who was treated with bilateral electrical stimulators, which were stereotactically placed in the anterior limbs of the internal capsules. Following psychiatric consultation and 10 years of empirical medication regimens for OCD, a woman was referred for neurosurgical evaluation. After informed consent had been obtained from the patient, the authors placed bilateral stimulator leads in the anterior limbs of the internal capsules. The stereotactic coordinates were based on data in pertinent current literature. The stimulation parameters, which are presented in this paper, were set at 2 weeks and reviewed at 6 weeks and 3 months postoperatively. No changes were required. Postoperative analysis included evaluation by the patient's referring psychiatrist, a second independent psychiatrist, and pre- and postoperative administration of the Yale-Brown Obsessive Compulsive Scale. A marked improvement was noted in thispatient's OCD symptomatology and general psychosocial function. Previous documentation of patient responses to psychosurgical procedures for intractable or refractory OCD has been met with little enthusiasm, presumably because of the invasiveness and irreversibility of the surgery. In this report the authors suggest that deep brain stimulation of appropriate targets may be an effective and safe treatment for certain patients with OCD and a potentially reversible treatment for those patients who do not obtain therapeutic benefit.

Adult↗
PubMed2004

White matter hemisphere asymmetries in healthy subjects and in schizophrenia: a diffusion tensor MRI study.

Hemisphere asymmetry was explored in normal healthy subjects and in patients with schizophrenia using a novel voxel-based tensor analysis applied to fractional anisotropy (FA) of the diffusion tensor. Our voxel-based approach, which requires precise spatial normalization to remove the misalignment of fiber tracts, includes generating a symmetrical group average template of the diffusion tensor by applying nonlinear elastic warping of the demons algorithm. We then normalized all 32 diffusion tensor MRIs from healthy subjects and 23 from schizophrenic subjects to the symmetrical average template. For each brain, six channels of tensor component images and one T2-weighted image were used for registration to match tensor orientation and shape between images. A statistical evaluation of white matter asymmetry was then conducted on the normalized FA images and their flipped images. In controls, we found left-higher-than-right anisotropic asymmetry in the anterior part of the corpus callosum, cingulum bundle, the optic radiation, and the superior cerebellar peduncle, and right-higher-than-left anisotropic asymmetry in the anterior limb of the internal capsule and the anterior limb's prefrontal regions, in the uncinate fasciculus, and in the superior longitudinal fasciculus. In patients, the asymmetry was lower, although still present, in the cingulum bundle and the anterior corpus callosum, and not found in the anterior limb of the internal capsule, the uncinate fasciculus, and the superior cerebellar peduncle compared to healthy subjects. These findings of anisotropic asymmetry pattern differences between healthy controls and patients with schizophrenia are likely related to neurodevelopmental abnormalities in schizophrenia.

Adult↗
PubMed1978

Comparative microangiographic and histologic studies of the embryonal development of intracerebral capillaries.

In 69 embryos and fetuses of cattle and pigs with an age of gestation of 4 weeks to 4 months the development of intracerebral capillaries was studied comparatively by microangiography and controlled by histologic slices. The first invasion of blood vessels into the wall of the neural tube takes place in the brain stem and colliculus ganglionaris at an age of gestation of 4 weeks. After that, specific and different angioarchitectonic patterns of capillary development can be demonstrated within the telencephalon, basal ganglia, and brain stem. The telencephalic vessels show concentrically arranged areas of ramification which interrupt their longitudinal course towards the ventricular cavity. The branchings are related topographically to the projection fibers from the internal capsule and to the subependymal matrix layer. In the basal ganglia, the developing internal capsule interrupts the blood supply of the caudate nucleus from the periphery, and a new central system is established mainly running radially towards the ventricular canal. Thus, it could be shown in consecutive stages of cerebral development that the angioarchitectonic pattern of a certain embryonal stage and brain area depends on the histologic structure of the neural tissue and its specific metabolic demands.

Animals↗
PubMed1990

[The MR evaluation of normal children and disorders of neuronal migration and myelination].

We often experience the case that is difficult to differentiate normal from abnormal myelinating process by CT scan, because the diagnosis of myelinating maturation of the infant during developmental process is confusing. We can understand maturation of myelination adding to the advancement of diagnostic resolution by MR imager. So we obtain more informations about the abnormality of myelination and development of the brain by MR imaging than CT scan. This study demonstrates the ability of MR imaging to show progression of myelination in 10 infants and children. We also reveals the patients with disorders of neuronal migration or myelination during developing process. MR scanning could be obtained by sedation using such as triclofos or chloral hydrate for infant and younger children. It was necessary to use diazepam or pentazocine intravenously for elder children with mental retardation or restlessness. MR scans were performed with Siemens MAGNETOM 1.5 Tesla. T 1-weighted spin echo image (TR 600/TE 15) and T 2-weighted image (TR 3000/TE 90) were obtained for all cases. The ten normal infants and children (7 boys, 3 girls) were aged from 1 month to 4 years. Maturation of white matter generally proceeded from posterior limb of internal capsule to middle cerebellar peduncle, cerebellar white matter, corpus callosum, anterior limb of internal capsule, occipital white matter, centrum semiovale, finally frontal white matter. Myelination was matured during the first two years by T 2-weighted images. Changes caused by brain myelination were seen earlier on T 1-weighted images (7 months after birth) than on T 2-weighted images (one year and 9 months after birth).(ABSTRACT TRUNCATED AT 250 WORDS)

Brain↗
PubMed1997

Microscopic study of muscle spindles in recti muscles of human fetal eye.

Muscle spindles of recti muscles of the eyebulb appear in the 11th week of intrauterine life. At first, the spindle manifests the stage of myotube with 2-3 intrafusal fibers and is surrounded by the monolayer of internal capsule. In the course of subsequent development, the number of intrafusal fibers increases. Internal capsule begins to demonstrate two layers (14th week) and, then, external capsule develops (17th week). In the 20th week, mature spindles have been observed with a multilayered external capsule.

Embryonic and Fetal Development↗