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PubMed1998

Treatment with AC pulsed electromagnetic fields normalizes the latency of the visual evoked response in a multiple sclerosis patient with optic atrophy.

Visual evoked response (VER) studies have been utilized as supportive information for the diagnosis of multiple sclerosis (MS) and may be useful in objectively monitoring the effects of various therapeutic modalities. Delayed latency of the VER, which reflects slowed impulse transmission in the optic pathways, is the most characteristic abnormality associated with the disease. Brief transcranial applications of AC pulsed electromagnetic fields (EMFs) in the picotesla flux density are efficacious in the symptomatic treatment of MS and may also reestablish impulse transmission in the optic pathways. A 36 year old man developed an attack of right sided optic neuritis at the age of 30. On presentation he had blurring of vision with reduced acuity on the right and fundoscopic examination revealed pallor of the optic disc. A checkerboard pattern reversal VER showed a delayed latency to right eye stimulation (P100 = 132 ms; normal range: 95-115 ms). After he received two successive applications of AC pulsed EMFs of 7.5 picotesla flux density each of 20 minutes duration administered transcranially, there was a dramatic improvement in vision and the VER latency reverted to normal (P100= 107 ms). The rapid improvement in vision coupled with the normalization of the VER latency despite the presence of optic atrophy, which reflects chronic demyelination of the optic nerve, cannot be explained on the basis of partial or full reformation of myelin. It is proposed that in MS synaptic neurotransmitter deficiency is associated with the visual impairment and delayed VER latency following optic neuritis and that the recovery of the VER latency by treatment with pulsed EMFs is related to enhancement of synaptic neurotransmitter functions in the retina and central optic pathways. Recovery of the VER latency in MS patients may have important implications with respect to the treatment of visual impairment and prevention of visual loss. Specifically, repeated pulsed applications of EMFs may maintain impulse transmission in the optic nerve and thus potentially sustain its viability.

Adult↗
PubMed2002

Nonperioperative strokes in children with central nervous system tumors.

BACKGROUND: Nonperioperative strokes are rare yet potentially devastating events for children with central nervous system (CNS) tumors. The incidence of and risk factors for nonperioperative strokes in children with CNS tumors is unknown. METHODS: The authors performed a retrospective review of children from their institution with CNS tumors. The incidence of stroke in the nonperioperative period and the influence of patient demographic factors, coexisting genetic diseases, tumor type, and treatment modality on the subsequent occurrence of a stroke were determined. RESULTS: Eight hundred seven consecutive patients from the authors' institution with CNS tumors were observed for a combined 3224 nonperioperative years. Thirteen patients (1.6%) had a nonperioperative stroke, for an incidence of 4.03 strokes/1000 years of nonperioperative patient follow-up. Eight patients were males, and the median age at diagnosis of a CNS tumor was 4.8 years (range, 0.3-18.6 years). The median duration from diagnosis of a CNS tumor until the occurrence of stroke was 2.3 years (range, 0.3-15.8 years). Among numerous potential risk factors individually examined by chi-square analysis, only treatment with radiation therapy was associated with the subsequent development of a stroke (chi-square, P = 0.007). By logistic regression analysis, treatment with radiation therapy and a diagnosis of an optic pathway glioma were the only statistically significant variables associated with a stroke. CONCLUSIONS: Strokes are much more common among children with CNS tumors. Children treated with radiation therapy and those with optic pathway gliomas have a higher association with the occurrence of a subsequent nonperioperative stroke. Because children with optic pathway gliomas may be at particularly high risk of stroke after radiation therapy, the desired beneficial therapeutic effects of irradiation must always be weighed against its potentially adverse effects, including stroke.

Adolescent↗
PubMed2001

Ascites following ventriculoperitoneal shunting in children with chiasmatic-hypothalamic glioma.

OBJECT: Optic pathway gliomas in children can involve the optic nerve, chiasm, and hypothalamus. This uncommon, slowly growing tumor can cause hydrocephalus, which usually requires placement of a ventriculoperitoneal (VP) shunt. Symptomatic ascites may occasionally develop as a complication of the VP shunt procedure. The purpose of this study was to assess the risk factors associated with CSF ascites in children with optic pathway gliomas. METHODS: Twenty-two children (ages 4 months to 20 years) with chiasmatic-hypothalamic optic gliomas participated in this study. Four children were diagnosed with a chiasmatic glioma, 7 with a hypothalamic glioma, and 11 with a glioma involving both the optic chiasm and hypothalamus. Twelve children (55%) developed hydrocephalus and required VP shunt placement. Of the 12 shunted children, 4 (33%) developed CSF ascites. The incidence of ascites was not associated with infection, tumor metastasis, or multiple shunt revisions. There was no correlation with the size of the tumor. All 4 children with ascites had tumor involving the optic chiasm or optic nerve. None of the 5 children with pure hypothalamic glioma who underwent VP shunt placement have developed ascites. Among the 7 children suffering from chiasmatic or optic nerve gliomas who developed hydrocephalus, the risk of developing ascites as a complication of VP shunt placement was 57% (4/7). Ventriculoatrial (VA) shunt was the treatment of choice for children with VP shunt-induced ascites. After placement of a VA shunt the ascites subsided. The children did not develop further complications. CONCLUSION: We conclude that glioma involving the optic chiasm or nerve is associated with a high risk of developing ascites following VP shunt placement. VA shunt may be the treatment of choice for children with chiasmatic or optic nerve gliomas who require a CSF diversion procedure.

Adolescent↗
PubMed1999

Intracranial gliomas in neurofibromatosis type 1.

Optic pathway gliomas and brainstem gliomas are the predominant intracranial neoplasms associated with neurofibromatosis type 1 (NF1). Before the past 15 years, studies of optic pathway gliomas in NF1 were hampered by the inaccurate diagnosis of NF1, the unavailability of noninvasive neuroimaging techniques, and the frequent rendering of what would now be considered unnecessary, overly aggressive therapy. When studied systematically, these tumors behave in a much more benign fashion than their counterparts in children who do not have NF1. While they may cause symptoms in as many of 50% of cases, progression to the point where specific intervention is deemed necessary is unusual. Consequently, screening neuroimaging of asymptomatic patients is unwarranted. Because optic pathway tumors universally arise in children younger than 7 years of age, all such children should undergo yearly ophthalmologic evaluations and annual assessments of growth to monitor for signs of precocious puberty. Am. J. Med. Genet. (Semin. Med. Genet.) 89:38-44, 1999.

Brain Neoplasms↗
PubMed2003

Prognostic factors of CNS tumours in Neurofibromatosis 1 (NF1): a retrospective study of 104 patients.

In addition to multiple peripheral neurofibromas, Neurofibromatosis 1 (NF1) predisposes to CNS tumours. Most of them are pilocytic astrocytomas, arise in children and are located in the optic pathways or in the brainstem. The majority are indolent, but factors predictive of poor prognosis have yet to be identified. Furthermore, the incidence and natural history of gliomas of a higher grade, arising in adults or involving other locations are largely unknown in NF1. In order to address these issues, we performed a retrospective study of 104 patients followed in seven French centres between 1982 and 2000. Inclusion criteria were a diagnosis of NF1, according to the National Institutes of Health criteria, and the presence of a CNS tumour, regardless of type, location or age of onset. The series included 88 children (age range 3 months to 17 years) and 16 adults (age range 19-52 years). The median follow-up was 5.6 years. One hundred and twenty-seven CNS tumours were observed in the 104 patients. Eighty-four (66%) were optic pathway tumours (OPT) and 43 (34%) extra-optic pathway tumours (extra-OPT) (brainstem: n = 21; other locations: n = 22). Twenty-one patients (20%) had multiple CNS tumours. OPT were symptomatic in 50 patients and extra-OPT in 19. Main clinical findings at presentation included visual loss (n = 29; 58%) and precocious puberty (n = 5; 10%) for OPT, increased intracranial pressure (n = 9; 48%) for extra-OPT. Fourteen out of the 27 symptomatic tumours with histology were pilocytic astrocytomas. The overall survival rate was 90% at 5 years (95% confidence interval 82-95%). Extra-optic location, tumour diagnosis in adulthood and symptomatic tumours were independent factors associated with shorter survival time (P < 0.05, Cox model). Radiotherapy for OPT was associated with vascular complications (ischaemic strokes) and growth hormone deficiency in 32 and 46% of patients, respectively. In conclusion, mortality is high in extra-OPT, particularly in adults, whereas OPT are only exceptionally life-threatening. Radiotherapy of OPT is associated with an important morbidity in NF1.

Adolescent↗
PubMed1993

Optic nerve degeneration induces the expression of MHC antigens in the rat visual system.

The brain has long been considered to be an immunologically privileged site. However, privilege is not absolute, as has been shown by the inability of foreign tissue grafts to survive indefinitely in the brain. The rejection of this tissue is accompanied by the upregulation of major histocompatibility complex (MHC) antigen expression. Therefore it is essential to define conditions that influence the expression of these antigens in the brain, especially since such a definition may further the understanding of disease processes that lead to the autoimmune destruction of the central nervous system. Here we show that both MHC class I and class II antigens are expressed within 1 or 2 days of eye removal by cells showing the morphological characteristics of microglia. Expression is seen along the optic pathway and within the brainstem centers to which optic axons project. In the early stages of the reaction, MHC class I antigen expression is seen throughout the optic pathway, including the terminal distribution areas of the subcortical visual centers, while MHC cells class II are localised mainly to degenerating myelinated fiber systems. These changes are not accompanied by any alteration in the integrity of the blood-brain barrier. During the second week postlesion, class I positive cells are found beyond the confines of the degenerating pathways, while class II positive cells are seen within regions such as the stratum griseum superficiale of the superior colliculus, where few myelinated axons are present. There is subsequent diminution of MHC positive cells, but a small number of cells are still seen 60 days post-lesion. Focal lesions within the eye show that at early survival times, while class I MHC positive cells are distributed throughout the nerve, class II positive cells are largely absent from the unmyelinated segment of the nerve. Retrograde changes in the retina after nerve section are accompanied only by MHC class I antigen expression. These observations show that neural degeneration is accompanied by a rigid sequence of events involving expression of MHC antigens by microglia. If foreign antigens were present in the brain while these events were taking place, it is possible that such antigens would be recognised and destroyed by the host immune system.

Animals↗
PubMed2004

A fast visual evoked potential method for functional assessment and follow-up of childhood optic gliomas.

OBJECTIVE: To evaluate a fast technique of visual evoked potentials (VEPs) recording, in response to steady-state luminance stimuli (SS-LVEPs), for functional assessment and follow-up of childhood optic gliomas (OGs). METHODS: Eighteen OG patients (age range: 3.5-18 years), with different degrees of optic pathway damage severity, were examined. Sixteen age-matched normal subjects served as controls. Ten of the 18 OG patients were re-tested 1-3 months after the first examination. SS-LVEPs were elicited by a sinusoidally-modulated flickering (8 Hz) uniform field, generated by a light emitting diode (LED)-array and presented monocularly in a mini-ganzfeld. Amplitude and phase of the Fourier-analyzed response fundamental (1F) and second harmonic (2F) were measured. The full VEP protocol had a median duration of 6 min (range: 4-12). RESULTS: When compared to normal control values, median 1F and 2F SS-LVEP amplitudes of OG patients were reduced (P<0.01), with a borderline increase in 2F phase lag (P<0.05). In 11 OG patients with asymmetric optic pathway damage in between-eye comparisons, median 1F amplitude losses were greater (P<0.01) in fellow eyes with more severe damage. No significant interocular difference was observed in control subjects. Median test-retest changes of 1F and 2F component were <20% and 30 degrees for amplitude and phase, respectively. In individual OG patients, 1F and 2F amplitudes were positively correlated (P<0.01) with visual acuity. 1F amplitude losses were correlated (P=0.01) with the severity of optic disc atrophy. Considering both 1F and 2F abnormalities, diagnostic sensitivity of SS-LVEP in detecting OG-induced optic pathways damage was 83.3%. CONCLUSIONS: The present findings support the use of this technique, as an alternative to pattern VEPs, for functional assessment and follow-up of OG in uncooperative children.

Adolescent↗
PubMed2002

Conformal proton radiation therapy for pediatric low-grade astrocytomas.

BACKGROUND: To evaluate the safety and efficacy of proton radiation therapy (PRT) for intracranial low-grade astrocytomas, the authors analyzed the first 27 pediatric patients treated at Loma Linda University Medical Center (LLUMC). PATIENTS AND METHOD: Between September 1991 and August 1997, 27 patients (13 female, 14 male) underwent fractionated proton radiation therapy for progressive or recurrent low-grade astrocytoma. Age at time of treatment ranged from 2 to 18 years (mean: 8.7 years). Tumors were located centrally (diencephalic) in 15 patients, in the cerebral and cerebellar hemispheres in seven patients, and in the brainstem in five patients. 25/27 patients (92%) were treated for progressive, unresectable, or residual disease following subtotal resection. Tissue diagnosis was available in 23/27 patients (85%). Four patients with optic pathway tumors were treated without histologic confirmation. Target doses between 50.4 and 63.0 CGE (Cobalt Gray Equivalent, mean: 55.2 CGE) were prescribed at 1.8 CGE per fraction, five treatments per week. RESULTS: At a mean follow-up period of 3.3 years (0.6-6.8 years), 6/27 patients experienced local failure (all located within the irradiated field), and 4/27 patients had died. By anatomic site these data translated into rates of local control and survival of 87% (13/15 patients) and 93% (14/15 patients) for central tumors, 71% (5/7 patients) and 86% (6/7 patients) for hemispheric tumors, and 60% (3/5 patients) and 60% (3/5 patients) for tumors located in the brainstem. Proton radiation therapy was generally well tolerated. All children with local control maintained their performance status. One child with associated neurofibromatosis, Type 1, developed Moyamoya disease. All six patients with optic pathway tumors and useful vision maintained or improved their visual status. CONCLUSIONS: This report on pediatric low-grade astrocytomas confirms proton radiation therapy as a safe and efficacious 3-D conformal treatment modality. Results are encouraging for central tumors as well as large optic pathway tumors, where dose conformity is of particular importance; yet it is difficult to achieve. Longer follow-up time is needed to fully evaluate the benefits of normal tissue sparing.

Adolescent↗
PubMed1981

[Exploration of the optic and somatosensory pathways with cerebral evoked potentials].

Visual and somatosensorial evoked potentials are the electrical response, recorded on the scalp, that follows the presentation of visual and sensorial stimuli. After briefly mentioning the technical premises enabling evoked responses to be obtained from EEC activity, some cases are reported (demyelining, degenerative, compressive, ischaemic, anoxic pathology) where visual or sensory evoked potentials presented changes, proof of the usefulness of these techniques for the purposes of clinical documentation or for diagnosis in different fields of DNS pathology.

Brain↗
PubMed2006

[Guidance of regenerative axons in optic nerve regeneration in Bcl-2 overexpressing mice].

OBJECTIVE: To determine whether optic nerve can regenerate after optic nerve crush and weather the regenerating axon reaches the target in the brain in Bcl-2 overexpressing mice. METHODS: Left eye optic nerve crush was performed in wild-type (C57Bl/6J) and Bcl-2 transgenic mouse pups at 3 days after birth (P3), followed immediately by the opposite eyeball enucleated. Mouse pups were killed at 4 days post-surgery. Optic nerve regeneration was assessed at the sections of optic nerve and the brain. An anterograde tracer, cholera toxin B subunit conjugated with fluorescein (CTB-F), was applied intraocularly, immediately after optic nerve crush to label retinal ganglion cell axons. Immunofluorescence staining with anti-GAP-43 was carried out to reveal regenerating axons in optic nerve sections. RESULTS: In wild-type mice, severed optic nerves failed to regenerate. In contrast, in all of the Bcl-2 transgenic mice examined, optic nerves regenerated robustly over long distances, but the regenerating fibers were found to deviate from the optic pathway and grew into the forebrain to form aberrant projection. CONCLUSION: When the opposite eyeball is removed in P3 Bcl-2 overexpressing mice with optic nerve was crushed in one side, the guidance from the normal optic pathway is lost, the optic nerve could regenerate and reach the brain, but the regenerating axons could not reach both side of target in the midbrain, they grow into aberrant place of forebrain.

Animals↗
PubMed1989

[Compression of structures in the visual pathway by arteries of the circle of Willis in suprasellar tumors].

The mechanical compression of optic nerves, of the chiasma of optic pathways by vessels of Willis circle was revealed in 12 of 34 necropsies of extensive craniopharyngiomas and pituitary adenomas and in three of 109 patients operated on account of these tumours. The localization of pressure changes, from shallow grooves on the surface of optic structures to almost complete interruption of their anatomical continuity, depended on the localization of the tumour in relation to the chiasma. This relation was influenced in particular by two factors, the site of the primary development of the tumour and the premorbid localization of the chiasma. Impaired optic functions were the result of the action of pressure of the tumour exerted on the area and pressure of firm vascular structures on a defined portion of the optic pathway, which begins to act only when the tumour is large and has a more malignant effect than the pressure of the tumour itself.

Circle of Willis↗
PubMed2006

Pattern-reversal visual evoked potentials in patients with human T-lymphotropic virus type 1 uveitis.

PURPOSE: The purpose of this study was to evaluate the possible injury in the optic pathway by measuring P100 peak latency of pattern-reversal visual evoked potentials (PVEPs) in patients with human T-lymphotropic virus type 1 uveitis (HU). METHODS: The P100 peak latency of PVEP was measured during the period without macular abnormalities observed by fluorescein angiography in 23 patients (46 eyes) with HU and 24 patients (48 eyes) with Vogt-Koyanagi-Harada disease (VKH) with a corrected visual acuity of 20/25 or more. To determine the normal upper limit of P100 peak latency, PVEPs were measured in 31 normal subjects (31 eyes). In addition, in the HU patients, the serum anti-HTLV-1 antibody titer was measured by particle agglutination assay within 3 months of PVEP recording, and the period of HU was retrospectively surveyed. RESULTS: Delayed latency was observed in 4 (7 eyes) of the 23 patients (46 eyes) with HU but none of the 24 patients (48 eyes) with VKH. All four patients with delayed latency showed a serum anti-HTLV-1 antibody titer of more than x4000. The HU period in the HU patients was 0.2-14.0 years, and the HU periods in the four patients with delayed latency were 0.8, 2.7, 4.2, and 14.0 years, respectively. CONCLUSIONS: We measured pattern-reversal visual evoked potentials and observed delayed P100 peak latency in 7 of the 46 eyes in 4 (17.4%) of the 23 HU patients. This suggests injury in the optic pathway including the optic nerve by HTLV-1 in some patients with HU. In the future, consideration should also be given to the possible development of optic neuropathy due to HTLV-1.

Adolescent↗
PubMed1985

Growth cones of developing retinal cells in vivo, on culture surfaces, and in collagen matrices.

The outgrowth of axons from the early retina in vivo is compared with that from retinal explants in two types of culture systems. The normal time course of axonal growth along the primordial optic pathway to the optic tectum is characterized, using tritiated proline and horseradish peroxidase (HRP) as anterograde tracers. The rate of axonal elongation in vivo is estimated to be about 32 micron/hr at 22 degrees C. The HRP technique allows visualization of retinal growth cones in vivo. Observations can thus be made on their microanatomy and on the environment through which they navigate. The growth cones of retinal ganglion cells in the embryo have lamellipodia and fairly short filopodia (approximately 10 micron) which are directed forward. The growth cones are found near the pial surface of the brain but do not seem to maintain contact with it. Two culture systems were developed to investigate axonal pathways in vitro. In the first, different substrates and culture media were explored. Results indicate that growth cones prefer a polyornithine substrate over a collagen one. The media that promotes the best neurite outgrowth consists of L15 (60%), fetal calf serum (10%) and Xenopus embryo extract (1 mg/ml). Time-lapse video monitoring of substrate cultures reveals an average rate of outgrowth of about 18 micron/hr with great variability. The growth cones in these cultures are large, flattened, and complex compared to those in vivo, and their filopodia extend in many different directions. The second culture system is a collagen gel infiltrated with growth medium. In these conditions neurite outgrowth more closely mimics that in vivo. The rate is faster than on substrates, and the growth cones appear morphologically similar to those in the embryo. Preliminary experiments using the gel culture system to test for chemotaxis of retinal axons toward their targets failed to demonstrate such an effect.

Animals↗
PubMed1987

Visual evoked potential in the management of pituitary tumor during pregnancy.

We examined a pregnant woman with chiasmal syndrome in the late stage of pregnancy. Her vision was determined to be seriously threatened after 31 weeks' gestation. Study of the latency of preoperative visual evoked potentials (VEPs) in other patients with pituitary tumor showed that insofar as latency is not delayed, surgical decompression is expected to be followed by functional improvement of the optic pathway. We monitored optic nerve function by serially recorded VEPs, and labor was induced at 38 weeks because there had been no delayed response up to that time. After a decompressive operation, visual field and visual acuity recovered normally. Serially recorded VEPs can provide a useful monitor along with visual field and acuity tests in guiding therapy for a patient with threatened vision in late pregnancy and in determining whether or when to induce labor.

Adenoma↗
PubMed2001

Differential activation of microglial cells in local and remote areas of IRBP1169-1191-induced rat uveitis.

Using a Lewis rat model of interphotoreceptor retinoid binding protein (IRBP)-induced experimental autoimmune uveitis (EAU) we examined cellular reactions in the optic pathway (retina, choroid, optic nerve, optic tract, colliculus superior, and visual cortex). Two to six animals were studied at days 0, 7, 9, 11, 12, 13, 14, 18 and 22 after immunization by immunohistochemistry with monoclonal antibodies against ED , ED2, OX6, OX22, EMAP II, AIF-1 and W3/13. In the retina, choroid and distal optic nerve increased immunoreactivity to ED1, OX6, OX22, EMAP II, AIF-1 and W3/13 was initially observed at day 9, peaked at days 13-14 and diminished rapidly from day 18 onwards. No changes were seen in the density of ED2-positive resident macrophages. In the optic tract, ED1 and OX6 expression was induced in microglial cells beginning with day 11 and persisted until day 22. AIF-1, EMAP II and ED2 expression was not visibly up-regulated and no lymphocytic infiltrates (OX22-, W3/13-positive cells) were observed. In the central projection fields, no cellular reaction could be found. Thus, cellular response in IRBP-induced rat uveoretinitis is not restricted to the eye. Microglial activation is also seen in the distal optic nerve and optic tract. This remote microglial activation, however, differs in intensity, time course and expression of activation markers, thus indicating different activation cascades. The mild remote microglial activation is probably due to neuronal-microglial interactions resulting from neuronal damage in the retinal ganglion cell layer and nerve fiber layer with consecutive axonal degeneration and not from an inflammatory reaction as seen in the eye.

Animals↗
PubMed2001

Evaluation of a leaf position optimization tool for intensity modulated radiation therapy of head and neck cancer.

BACKGROUND AND PURPOSE: Since 1996, patients are treated at Ghent University Hospital with a multi-segment technique using MultiLeaf Collimators. The segments were obtained by using the Beam's eye view projections of the planning target volume (PTV) and the organs at risk (OARs), after which the segments weights were optimized. To investigate if optimization of the leaf positions would further improve the intensity modulated radiation therapy (IMRT) plans, a tool optimizing leaf positions and segment weights simultaneously, was developed. This tool is called SOWAT, which is the acronym for segment outline and weight adapting tool. MATERIAL AND METHODS: The tool evaluates the effects of changing the position of each collimating leaf of all segments on the value of the objective function. Only changes that improve the value of the objective function are retained. Between December 1999 and January 2001, 30 head and neck patients were treated with IMRT. Two patient groups were distinguished: pharyngeal and laryngeal tumors (n=17) and sinonasal tumors (n=13). A specific set of physical endpoints was evaluated for each group. Dose statistics of the treatment plans without and with SOWAT were analyzed. RESULTS: When using SOWAT for the pharyngeal and laryngeal cases, the PTV dose homogeneity increased with a median of 11% (range 2-27%), while the maximum dose to the spinal cord was decreased for 14 of the 17 patients. In four plans where parotid function preservation was a goal, the parotid mean dose was lower than 26 Gy in one plan without SOWAT, and in four plans with SOWAT. For the sinonasal tumors, the PTV dose homogeneity increased with a median of 7% (range 1-14%). SOWAT lowered the mean dose to 53 of the 63 optic pathway structures (retina, optic nerve and optic chiasm). SOWAT leaves the number of segments unchanged and has little or no effect on the delivery time. CONCLUSIONS: SOWAT is a powerful tool to perform the final optimization of IMRT plans, without increasing the complexity of the plan or the delivery time.

Algorithms↗
PubMed1988

Disorders of histogenesis: the neurocutaneous syndromes.

MRI is uniquely suited to demonstration of the wide array of brain abnormalities in the neurocutaneous syndromes, due to its ability to provide previously unattainable neuroanatomic information on T1-weighted images and its extreme sensitivity to changes in water content of brain structures on T2-weighted images. It therefore is assisting physicians in better understanding the full expression of these heritable disorders, such as the extent of optic pathway involvement in optic nerve glioma, the presence of hamartomas in TS, and abnormal myelination in Sturge-Weber syndrome. It may in the future have a role in genetic counseling in TS. CT provides complimentary information to MRI in the evaluation of intracranial pathology in the neurocutaneous syndromes. Bone abnormalities and abnormal states of calcification may at times still be better evaluated by CT. Additionally, CT is a less expensive means of following existent abnormalities over time.

Angiomatosis↗
PubMed2006

Two optic flow pathways from the pretectal nucleus lentiformis mesencephali to the cerebellum in pigeons (Columba livia).

Neurons in the pretectal nucleus lentiformis mesencephali (LM) are involved in the analysis of optic flow. LM provides mossy fiber inputs to folia VI-VIII of the posterior cerebellum and IXcd of the vestibulocerebellum. Previous research has shown that the vestibulocerebellum is involved in visual-vestibular integration supporting gaze stabilization. The function of folia VI-VIII in pigeons is not well understood; however, these folia receive input from a tectopontine system, which is likely involved with analyzing local motion as opposed to optic flow. We sought to determine whether the mossy fiber input from LM to IXcd differs from that to VI-VIII. Fluorescent retrograde tracers were injected into these folia, and the pattern of labeling in LM was observed. Large multipolar neurons were labeled throughout the rostrocaudal extent of LM. There was a clear mediolateral difference: 74.3% of LM neurons projecting to IXcd were located in the lateral subnucleus of LM (LMl), whereas 73.8% of LM neurons projecting to VI-VIII were found in medial LM (LMm). This suggests that the subnuclei of LM have differing roles. In particular, the LMl-IXcd pathway is involved in generating the optokinetic response. We suggest that the pathway from LMm to VI-VIII is integrating optic flow and local motion to support various oculomotor and visuomotor behaviors, including obstacle avoidance during locomotion.

Animals↗