Neuroimaging of Neurocutaneous Diseases

The Vestibulocochlear Nerve: Anatomy and Pathology

The vestibulocochlear nerve is the eighth cranial nerve, entering the brainstem in the medullopontine sulcus after crossing the internal auditory canal and cerebellopontine angle cistern. It is a purely sensitive nerve, originating from the Scarpa's and spiral ganglions, responsible for balance and hearing. It has 6 nuclei located in the lower pons. Magnetic resonance imaging (MRI) is useful for evaluating the vestibulocochlear nerve, although computed tomography may have a complementary role in assessing bone lesions. A heavily T2-weighted sequence, such as fast imaging employing steady-state acquisition (FIESTA) or constructive interference steady state (CISS), is crucial in imaging exams to depict the canalicular and cisternal segments of the vestibulocochlear nerve, as well as the fluid signal intensity in the membranous labyrinth. The vestibulocochlear nerve can be affected by several diseases, such as congenital malformations, trauma, inflammatory or infectious diseases, vascular disorders, and neoplasms. The purpose of this article is to review the vestibulocochlear nerve anatomy, discuss the best MRI techniques to evaluate this nerve and demonstrate the imaging aspect of the main diseases that affect it.

Olfactory bulb enlargement in neurofibromatosis type 1: report of a novel finding

Neurofibromatosis type 1 (NF1) is a genetic autosomal dominant disease caused by mutation of the protein neurofibromin, a regulator of cell growth. The most frequent intracranial findings are unidentified bright objects (UBOs), thickening of the corpus callosum, sphenoid wing dysplasia, cerebral vasculopathy, optic and non-optic pilocytic astrocytomas, and plexiform neurofibromas. We report two cases of NF1 patients with asymptomatic olfactory bulbs (OBs) enlargement depicted with Magnetic Resonance Imaging (MRI). To the best of our knowledge, this finding has not been reported in the scientific literature so far. We hypothesize that olfactory bulbs enlargement may have a pathogenetic nature like that of the UBOs as in one of our patients there was spontaneous regression during follow-up. The olfactory bulbs enlargement expands the broad neuroradiological spectrum of finding of NF1. More reports are required to better understand incidence, pathogenesis, and clinical behavior of olfactory bulbs enlargement in NF1 patients.

The Forgotten Phacomatoses: A Neuroimaging Review of Rare Neurocutaneous Disorders

Phakomatoses, or neurocutaneous syndromes, are a heterogeneous group of rare genetic disorders that predominantly affect structures arising from the embryonic ectoderm, namely the skin, eye globe, retina, tooth enamel, and central nervous system. Other organs are also involved in some syndromes, mainly cardiovascular, pulmonary, renal, and musculoskeletal systems. Currently, more than sixty distinct entities belonging to this category have been described in the literature. Common phakomatoses include conditions like Neurofibromatosis and Tuberous sclerosis. Several review papers have focused on various aspects of these common conditions, including clinical presentation, genetic and molecular basis, and neuroimaging features. In this review, we focus on rare neurocutaneous syndromes: Melanophakomatoses (Ie, Neurocutaneous Melanosis, and Incontinentia Pigmenti), Vascular Phakomatoses (Ie, Ataxia Telangiectasia and PHACE Syndrome), and other conditions such as Cowden Syndrome, Basal Nevus Syndrome, Schwannomatosis, Progressive Facial Hemiatrophy, Gomez-Lopez-Hernandez Syndrome, Wyburn-Mason Syndrome, CHILD Syndrome, and Proteus Syndrome. We also review the neuroradiologic manifestations of these conditions as a guide for neurologists and neuroradiologists in their daily practice.

Optic Nerve Tortuosity in Neurofibromatosis Type 1: A Rare Case Report

Optic nerve tortuosity is a benign and usually asymptomatic optic nerve abnormality documented on magnetic resonance imaging. This abnormality has rarely been defined in neurofibromatosis type 1 (NF1) cases. In this case report, we present incidental optic nerve tortuosity in a housewife with NF1 without any ocular involvement. Optic nerve tortuosity may occasionally be an incidental finding in patients with NF1. Therefore, clinicians should be aware of this rare coexistence.

Diffusion-weighted imaging and diffusion tensor imaging as adjuncts to conventional MRI for the diagnosis and management of peripheral nerve sheath tumors: current perspectives and future directions

Peripheral nerve sheath tumors (PNSTs) account for ~ 5% of soft tissue neoplasms and are responsible for a wide spectrum of morbidities ranging from localized neuropathy to fulminant metastatic spread and death. MR imaging represents the gold standard for identification of these neoplasms, however, current anatomic MR imaging markers do not reliably detect or differentiate benign and malignant lesions, and therefore, biopsy or excision is required for definitive diagnosis. Diffusion-weighted MR imaging (DWI) serves as a useful tool in the evaluation and management of PNSTs by providing functional information regarding the degree of diffusion, while diffusion tensor imaging (DTI) aids in determining the directional information of predominant diffusion and has been shown to be particularly useful for pre-operative planning of these tumors by delineating healthy and pathologic fascicles. The article focuses on these important neurogenic lesions, highlighting the current utility of diffusion MR imaging and future directions including computerized radiomic analysis. KEY POINTS: • Anatomic MRI is moderately accurate in differentiating benign from malignant PNST. • Diffusion tensor imaging facilitates pre-operative planning of PNSTs by depicting neuropathy and tractography. • Radiomics will likely augment current observer-based diagnostic criteria for PNSTs.

MR imaging of neoplastic and non-neoplastic lesions of the brain and spine in neurofibromatosis type I

The aim of this work is to review the MR imaging of neoplastic and non-neoplastic lesions of the brain and spine in neurofibromatosis type I. Neoplastic lesions are optic pathway gliomas, brain stem gliomas, other gliomas of the brain, and peripheral nerve sheath tumors. Structural changes in the brain include unidentified bright objects, macrocephaly, and enlarged corpus callosum. Bony dysplasia changes as sphenoid ridge dysplasia, spinal scalloping, dural ectasia, and meningoceles. Vasculopathy and cortical cerebral and cerebellar malformations of the brain have been reported.

Incidental findings on routine brain MRI scans in preterm infants

OBJECTIVE

Many neonatal intensive care units (NICUs) have adopted the practice of performing routine brain MRI in very low birth weight (VLBW) infants at term-equivalent age in order to better evaluate prematurity-related acquired lesions. A number of unexpected brain abnormalities of potential clinical significance can be visualised on routine scans as well. The aim of our study was to describe these incidental findings (IFs) in a VLBW population and to assess their clinical significance.

STUDY DESIGN

We retrospectively reviewed a series of brain MRI scans performed in VLBW infants consecutively admitted to our NICU between November 2011 and November 2014. IFs on brain MRI, which were not detected by cranial ultrasound nor suspected clinically, were registered. Clinical significance of IF was assessed in terms of need of further diagnostic or therapeutic interventions.

RESULTS

IFs were detected in 28 out of 276 VLBW infants (10.1%). In total, 21 cases (7.6%) required an intervention, which was only diagnostic in 16 cases, and both diagnostic and therapeutic in 5 cases. In the remaining seven cases (2.5%), no further action was considered necessary.

CONCLUSIONS

This study suggests that IFs on brain MRI of VLBW infants are not rare. In our population, most of them required a diagnostic or therapeutic intervention. The need and appropriateness of routine MRI scanning in VLBW at term-equivalent age are still subject of debate, and we believe our data can contribute meaningfully to this discussion.

Metabolic, endocrine, and other genetic disorders

Metabolic, endocrine, and genetic diseases of the brain include a very large array of disorders caused by a wide range of underlying abnormalities and involving a variety of brain structures. Often these disorders manifest as recognizable, though sometimes overlapping, patterns on neuroimaging studies that may enable a diagnosis based on imaging or may alternatively provide enough clues to direct further diagnostic evaluation. The diagnostic workup can include various biochemical laboratory or genetic studies. In this chapter, after a brief review of normal white-matter development, we will describe a variety of leukodystrophies resulting from metabolic disorders involving the brain, including mitochondrial and respiratory chain diseases. We will then describe various acidurias, urea cycle disorders, disorders related to copper and iron metabolism, and disorders of ganglioside and mucopolysaccharide metabolism. Lastly, various other hypomyelinating and dysmyelinating leukodystrophies, including vanishing white-matter disease, megalencephalic leukoencephalopathy with subcortical cysts, and oculocerebrorenal syndrome will be presented. In the following section on endocrine disorders, we will examine various disorders of the hypothalamic-pituitary axis, including developmental, inflammatory, and neoplastic diseases. Neonatal hypoglycemia will also be briefly reviewed. In the final section, we will review a few of the common genetic phakomatoses. Throughout the text, both imaging and brief clinical features of the various disorders will be discussed.

A Classic Case of Tuberous Sclerosis with Multisystem Involvement Including Giant Bilateral Renal Angiomyolipomas Presenting as Massive Hematuria

Background

Tuberous Sclerosis (TSC) also known as Bourneville disease is a neurocutaneous syndrome having an autosomal dominant inheritance pattern, though the condition has a high rate of spontaneous mutation. It is the second most common neurocutaneous syndrome after neurofibromatosis. This disease demonstrates a widespread potential for hamartomatous growths in multiple organ systems.

Case Report

We report a case of a 36-year-old female with TSC presenting as massive hematuria with underlying giant bilateral renal angiomyolipomas (AML) with estimated total tumor burden of more than 8 kg which is to the best of our knowledge the highest ever reported. The patient also had lymphangioleiomyomatosis and lesions in the brain, skin, teeth and bones.

Conclusions

TSC has a wide variety of clinical and radiologic manifestations. It should be suspected when some of the common radiological manifestations are found, including CNS involvement, renal and hepatic AMLs and LAM, even if clinical signs are not obvious. Renal AMLs in setting of TSC may reach giant proportions and may present with massive hematuria.

Neuroimaging of phakomatoses: overview and advances

The phakomatoses are disorders characterized by multiple hamartomas and other congenital malformations affecting mainly the skin and the central and peripheral nervous systems. Many affected individuals have an increased genetic susceptibility to develop malignancies. Imaging is central in the diagnosis of many of the phakomatoses, and MRI is used as a screening tool in many children with known neurocutaneous disorders. This manuscript addresses the three most common (neurofibromatosis type 1, tuberous sclerosis complex, Sturge-Weber syndrome) and focuses on pathophysiological and radiologic insights that have emerged in the last few years.