Reversal of optic canal stenosis in osteopetrosis after bone marrow transplant

Three-dimensional anatomical analysis of the optic nerve canal with virtual model based on CBCT

The optic nerve canal (ONC) is a fine skeletal structure that contains the optic nerve. However, it has not been thoroughly examined. This necessitates establishing a baseline knowledge of the geometrical and volumetric parameters of the ONC. The data of twenty patients who received a cone beam computed tomography examination were prepared using a voxel-based segmentation. The measurement was performed separately by two examiners on virtual skull models in stereolithography format in Geomagic Wrap®. The results showed that the volume of the ONC varied between 92.48 mm3 and 162.7 mm3 (M = 123.46 mm3, SD = 26.61 mm3). Sex-specific statistically significant differences in volume were detected only for the right side. The angle of the ONC to the skull base was independent of the diameter of the canal. Both the intrarater and interrater comparisons of the measurements showed high values of reproducibility of the results. This study showed that a virtual anatomical model provides a feasible and reliable method to investigate the ONC. The examination technique could have a wider range of application in anthropology and application in clinical medicine. Advances in the automation of radiological diagnostics and the digital analysis of X-ray images could help to reduce examination times.

Phenotype-autosomal recessive osteopetrosis

Osteopetrosis (OPT) is a life-threatening disease characterized by increased bone mass caused by diminished osteoclast function/differentiation. The autosomal recessive forms, caused by biallelic variants in implicated genes, usually present in infancy. Without treatment, autosomal recessive OPTs are usually fatal within the first 10 years of life [1]. Here, we review the clinical features and associated pathophysiology of the autosomal recessive OPT. A greater understanding of these rare disorders will advance early diagnosis and optimal management.

Findings on Optical Coherence Tomography in Malignant Infantile Osteopetrosis

Malignant infantile osteopetrosis is a rare inherited disorder with neurological complications and a shortened life expectancy. Vision loss is typically attributed to osseous compression of the optic nerves at the level of the optic canal. Fundus imaging is reported, as well as the first optical coherence tomography and optical coherence tomography angiography in this rare condition. Imaging revealed optic nerve pallor, subfoveal ellipsoid zone disruption, and an enlarged foveal avascular zone. These results provide insight regarding other potential mechanisms of vision loss in these patients. [Ophthalmic Surg Lasers Imaging Retina 2022; 53:398-402.].

Optic Canal Diameters According to Age in the Pediatric Population

PURPOSE

To determine the normal range of optic canal diameters in the Turkish pediatric population.

METHODS

Brain, orbital, and maxillofacial computed tomography examinations were evaluated retrospectively. Children with cranial bone disorders affecting the bone structure of the optic canal were excluded from the study. Oblique axial and oblique sagittal multiplanar reformatted images were created in accordance with the axis of the optic canal on both sides, and measurements were taken from the shortest transverse and craniocaudal diameters of the optic canal in these images.

RESULTS

Two hundred computed tomography examinations were evaluated. One hundred two of the patients were female and the rest were male. Patient ages ranged from 1 to 211 months (mean ± standard deviation: 86.42 ± 65.39 months). There was no significant difference between the transverse and craniocaudal optic canal diameters between sexes (P > .05). Therefore, the analyses were reevaluated in the entire patient series, regardless of sex. No significant correlation was found in the correlation test performed between optic canal diameters according to the age of the patients. No statistically significant difference was observed between the right and left optic canal diameters.

CONCLUSIONS

The determination of normal values of tissues, structures, and organs that differs with age has an important role in pediatric radiology. The authors believe that the determination of normal optic canal diameters according to certain age groups will meet the needs of daily practice. [J Pediatr Ophthalmol Strabismus. 2021;58(5):319-323.].

Comparison of Optic Canal Diameter in Children With Malignant Infantile Osteopetrosis and Normal Children and the Effects of Hematopoietic Stem Cell Transplantation on the Optic Canal Diameter

PURPOSE

To investigate the difference in the optic canal diameter between children with autosomal recessive malignant infantile osteopetrosis and normal children, and to assess the influence of hematopoietic stem cell transplantation on the optic canal diameter.

METHODS

Twenty pediatric patients with malignant infantile osteopetrosis and 22 normal control children were included in this study. Eleven patients with malignant infantile osteopetrosis underwent hematopoietic stem cell transplantation. The measurements included optical canal diameter and flash visual evoked potential. Comparisons of these measurements between patients with malignant infantile osteopetrosis and normal controls as well as before and after hematopoietic stem cell transplantation were performed. The correlation between age and optic canal diameter was analyzed using Pearson correlation analysis.

RESULTS

The mean optic canal diameter before hematopoietic stem cell transplantation was 1.65 ± 0.54 mm in patients with malignant infantile osteopetrosis and 3.38 ± 0.60 mm in the control group (P < .001). The mean optic canal diameter after hematopoietic stem cell transplantation was 2.72 ± 0.66 mm, which was significantly different from the pre-transplantation measurement (P < .001). The P2 latency for the flash visual evoked potential after hematopoietic stem cell transplantation (152.3 ± 36.4 ms) was significantly less than that before transplantation (165.5 ± 27.7 ms; P = .051). Pearson correlation analysis revealed a significant correlation between age and optic canal diameter (r = 0.722, P < .001).

CONCLUSIONS

The optic canal was narrower in pediatric patients with malignant infantile osteopetrosis than in age-matched normal controls. This condition can be relieved through hematopoietic stem cell transplantation and the impaired conductibility of the optic nerve can be improved in some cases. [J Pediatr Ophthalmol Strabismus. 2019;56(1):35-42.].

Impact of hematopoietic stem cell transplant on VEP and ABR values of the patients with malignant infantile osteopetrosis

OBJECTIVES

Malignant Infantile Osteopetrosis (MIOP) is a rare inherited disorder with neurological complications, notably visual impairment and decrease of hearing level. Although Hematopoietic Stem Cell Transplantation (HSCT) has been approved as the only curative treatment for these patients, the exact impact of it on visual and hearing level is still unclear.

STUDY DESIGN

We analyzed the P2 latency and amplitude from Visual Evoked Potentials (VEP) of 10 patients (20 eyes) and the threshold of wave V from Auditory Brainstem Response (ABR) of 15 patients (30 ears) with MIOP before, 6 and 12 months after HSCT.

RESULTS

Before the HSCT, 10/30 ears demonstrated some degree of hearing loss; while only 3/20 eyes had P2 wave latencies in normal range for age. Using GEE models, it was shown that 12 months after HSCT, wave V threshold of ABR of the patients was significantly lower compared to its value from before the transplant (p value: 0.04). The analysis of latency and amplitude of P2 wave of VEPs showed no significant difference between before and after the transplant.

CONCLUSION

This study clearly showed that HSCT can improve the hearing level of the patients in terms of ABR threshold. Although HSCT made no significant improvement in latency of P2 in VEP of the patients, it can be concluded that transplant can halt visual regression in these patients. Early diagnosis of MIOP with this objective tools and subsequently early HSCT in these patients can decrease the rate of neurological complications of MIOP and improve the quality of life in them.

Update on the application of optic nerve sheath fenestration

BACKGROUND

With the ongoing development of surgical procedures and instruments, the safety of optic nerve sheath fenestration (ONSF) has been improved.

OBJECTIVE

Through the past three decades, progress has been made in preventing visual loss from chronic optic nerve swelling in idiopathic intracranial hypertension (IIH), secondary intracranial hypertension and local optic nerve diseases. We now review the updated application of ONSF in those diseases.

METHODS

The application of ONSF in papilledema due to IIH, secondary intracranial hypertension to cerebral venous sinus occlusion, Cryptococcal meningitis, and intracranial mass or tumors is reviewed. Additionally, the potential benefits of ONSF in local optic neuropathy from optic nerve sheath meningioma, optic nerve drusen, traumatic optic neuropathy and optic nerve/sheath biopsy are also described.

RESULTS

Although ONSF has little or no effect on intracranial pressure, it is a safe, relative easy and effective surgical procedure to prevent or reverse visual loss in IIH. When other treatment modalities fail to timely protect vision, ONSF can be useful in protecting visual function or delay visual loss in secondary intracranial hypertension.

CONCLUSION

We recommend that ONSF should be considered as a meaningful alternative or an adjunct therapy to reduce or delay the visual morbidity of these diseases, although the use of ONSF for some of them remains controversial.

Proliferation and arrest: the genetics of orbital disorders

PURPOSE OF REVIEW

Oculoplastic genetic diseases can be divided into eyelid, lacrimal, and orbital disorders. The purpose of this review is to develop a rational approach to the categorization of genetic diseases that affect the orbit and review the most recent developments.

RECENT FINDINGS

Genetic disorders that affect the orbit can simply be divided into whether they cause proliferation or arrest of orbital structures. Proliferative conditions include vascular, neural, bony, mesenchymal, and lymphoid. Conditions that cause arrest can be subcategorized into whether they cause soft tissue or bony arrest of development. The genetics of many of these conditions have been elucidated and novel treatments, based on the molecular defects, have been utilized with some success.

SUMMARY

Molecular advances may result in substitution of a molecular categorization scheme for the one proposed in this manuscript. Delineation of the underlying molecular causes of these disorders will result in earlier, less invasive procedures than those that are currently employed.

A unifying theory for the multifactorial origin of cerebellar tonsillar herniation and hydrocephalus in osteopetrosis

OBJECT

Osteopetrosis is a rare congenital metabolic bone disease. There are very few reports in the literature associating cerebellar tonsillar herniation (CTH) and hydrocephalus requiring neurosurgical attention. The authors present cases of osteopetrosis requiring neurosurgical intervention from their practice and offer a detailed account of the literature.

METHODS

A retrospective review was conducted at the authors' institution, and all children with osteopetrosis requiring neurosurgical attention were identified. Medical charts and radiographic studies were reviewed. Data including age at presentation, sex, symptoms at presentation, age at follow-up, the presence of any neurological comorbidities, and surgical procedures performed were recorded.

RESULTS

Four patients were identified as having osteopetrosis requiring neurosurgical attention at the authors' institution between January 1, 2005, and January 1, 2014. There were 3 females and 1 male with an average age at presentation of 11.1 years; patients were observed for a mean of 4.4 years. All of the patients were identified as harboring jugular foraminal stenosis and CTH. Seventy-five percent of these patients developed hydrocephalus, and in those cases a triventricular pattern of dilation was noted. One patient developed syringomyelia. Three of the 4 patients underwent neurosurgical procedures. Cerebrospinal fluid diversion was performed in 2 patients via a ventriculoperitoneal shunt in one case and an endoscopic third ventriculostomy (ETV) in the other. The former patient required a proximal revision at 2 years for bony overgrowth at the site of the bur hole. Two patients underwent a suboccipital decompression. In patients undergoing CSF diversion, there was improvement in ventricle size.

CONCLUSIONS

Variable degrees of hindbrain crowding and/or CTH are mentioned throughout the literature, suggesting that this entity is nearly always present in this patient population. The progressive triventricular hydrocephalus seen in these cases results from a complex combination of both communicating and noncommunicating pathology, which may depend on the type of osteopetrosis, age at presentation, and the presence and degree of venous collateralization, and it appears that the hydrocephalus is more prevalent and more likely to be treated in infants and in the younger, school-aged population. The acquired hindbrain fullness in conjunction with the triventricular pattern of hydrocephalus has kept the authors enthusiastic regarding the use of ETV in these complicated cases.

An unusual cause of optic atrophy in a child

A 13-year-old child presenting with gross visual impairment was diagnosed as a case of optic atrophy. However, radiological investigations revealed osteopetrosis, which, though rare, can result in optic atrophy. The aim of this case report is to highlight this possibility while evaluating cases of optic atrophy in young patients.

Osteopetrosis

Osteopetrosis is a rare disease that occurs when a child has an unequal balance between new bone growth and elimination of old bone. Children with this entity are able to make new bone tissue, but are not able to break down and eliminate old bones, which is essential for normal bone growth. These thickened and enlarged bones are very weak. These children can exhibit: failure to thrive, macrocephaly, anemia, deafness, and blindness. We will present a case of osteopetrosis, esotropia, and amblyopia of a 7-year-old boy and will discuss the pathophysiology and treatment.

Spontaneous optic nerve compression in the osteopetrotic (op/op) mouse: a novel model of myelination failure

We report a focal disturbance in myelination of the optic nerve in the osteopetrotic (op/op) mouse, which results from a spontaneous compression of the nerve resulting from stenosis of the optic canal. The growth of the op/op optic nerve was significantly affected, being maximally suppressed at postnatal day 30 (P30; 33% of age matched control). Myelination of the nerve in the optic canal was significantly delayed at P15, and myelin was almost completely absent at P30. The size of nerves and myelination were conserved both in the intracranial and intraorbital segments at P30, suggesting that the axons in the compressed site are spared in all animals at P30. Interestingly, we observed recovery both in the nerve size and the density of myelinated axons at 7 months in almost half of the optic nerves examined, although some nerves lost axons and became atrophic. In vivo and ex vivo electrophysiological examinations of P30 op/op mice showed that nerve conduction was significantly delayed but not blocked with partial recovery in some mice by 7 months. Transcardial perfusion of FITC-labeled albumin suggested that local ischemia was at least in part the cause of this myelination failure. These results suggest that the primary abnormality is dysmyelination of the optic nerve in early development. This noninvasive model system will be a valuable tool to study the effects of nerve compression on the function and survival of oligodendrocyte progenitor cells/oligodendrocytes and axons and to explore the mechanism of redistribution of oligodendrocyte progenitor cells with compensatory myelination.

Optic canal diameter in infantile osteopetrosis

Infants with osteopetrosis may present early for ophthalmologic examination because of threatened visual impairment, primarily related to optic nerve compression. The authors describe two children with osteopetrosis who had narrow optic canals on orbital computed tomography. These canals were statistically narrower than those of newly developed, age-matched controls. Optic canal diameters, in addition to visual evoked potential data, may be helpful in determining prognosis.

Resolution of optic nerve edema and improved visual function after optic nerve sheath fenestration in a patient with osteopetrosis

PURPOSE

To describe the outcome of a patient with visual loss and optic nerve edema that resulted from osteopetrosis who underwent an optic nerve sheath fenestration (ONSF).

DESIGN

Interventional case report.

METHODS

A 33-year-old man with osteopetrosis had bilateral visual field loss and optic nerve edema. Computed tomography and magnetic resonance imaging demonstrated open optic canals. Although a lumbar puncture showed a normal opening pressure, there were other findings that were suggestive of increased intracranial pressure. The patient elected to undergo a unilateral optic nerve sheath fenestration.

RESULTS

After ONSF, the patient experienced markedly improved visual acuity, visual field, and optic nerve appearance.

CONCLUSION

Individuals with visual loss and optic disk edema that is associated with osteopetrosis may benefit from ONSF if the optic canals appear to be open and the optic nerve edema is thought to be related to increased intracranial pressure.

Surgical Correction of Craniosynostosis in Malignant Osteopetrosis

In osteopetrosis, bone healing is complicated by progressive sclerosis. A 2-year-old blind boy with malignant osteopetrosis developed increased intracranial pressure secondary to craniosynostosis. Osteopetrosis had already been treated with bone marrow transplantation (BMT), and bone remodeling seemed to be restored. A craniotomy was performed. The postoperative course and bone healing were uneventful. After successful BMT, craniofacial procedures seem to be possible without a high risk for osteomyelitis.

Neurological aspects of osteopetrosis

The osteopetroses are caused by reduced activity of osteoclasts which results in defective remodelling of bone and increased bone density. They range from a devastating neurometabolic disease, through severe malignant infantile osteopetrosis (OP) to two more benign conditions principally affecting adults [autosomal dominant OP (ADO I and II)]. In many patients the disease is caused by defects in either the proton pump [the a3 subunit of vacuolar-type H(+)-ATPase, encoded by the gene variously termed ATP6i or TCIRG1] or the ClC-7 chloride channel (ClCN7 gene). These pumps are responsible for acidifying the bone surface beneath the osteoclast. Although generally thought of as bone diseases, the most serious consequences of the osteopetroses are seen in the nervous system. Cranial nerves, blood vessels and the spinal cord are compressed by either gradual occlusion or lack of growth of skull foramina. Most patients with OP have some degree of optic atrophy and many children with severe forms of autosomal recessive OP are rendered blind; optic decompression is frequently attempted to prevent the latter. Auditory, facial and trigeminal nerves may also be affected, and hydrocephalus can develop. Stenosis of both arterial supply (internal carotid and vertebral arteries) and venous drainage may occur. The least understood form of the disease is neuronopathic OP [OP and infantile neuroaxonal dystrophy, MIM (Mendelian inheritance in man) 600329] which causes rapid neurodegeneration and death within the first year. Although characterized by the finding of widespread axonal spheroids and accumulation of ceroid lipofuscin, the biochemical basis of this disease remains unknown. The neurological complications of this disease and other variants are presented in the context of the latest classification of the disease.