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Rathke Cleft Cyst

Introduction Rathke cleft cysts are cystic sellar and suprasellar lesions arising from remnants of the embryonic Rathke pouch, a structure of ectodermal origin that folds superiorly from the pharynx during the fourth week of gestation. In the sella, Rathke pouch gives rise to the adenohypophysis anteriorly and intermediate lobe of the pituitary gland posteriorly. In the suprasellar cistern, Rathke pouch gives rise to the pars tuberalis.…

Partially Empty Sella

Introduction The empty sella turcica was first described in 1949 as a condition where the sella turcica is only partially filled by the pituitary gland, which appears flattened against the sellar floor ( Fig. 19.1 ). Autopsy studies confirm the high disease prevalence reported to be 5.5% to 20% of the general population. Not surprisingly, many patients who undergo brain imaging will have a partially empty…

Idiopathic Intracranial Hypertension (Pseudotumor Cerebri)

Introduction Idiopathic intracranial hypertension (IIH) is a disorder of elevated intracranial pressure (ICP) without apparent inciting etiology. Pseudotumor cerebri (PTC) is also a commonly accepted term describing the same disorder. Many authors advocate limiting the definition of IIH to a truly idiopathic subset of PTC, as PTC encompasses a list of known nontumor conditions resulting in elevated ICP, including the following: cerebrospinal fluid (CSF) malabsorption, superior…

Intracranial Hypotension

Introduction Intracranial hypotension is a clinical manifestation of low cerebrospinal fluid (CSF) volume or pressure caused by a dural CSF leak. It is usually precipitated by dural injury from an iatrogenic event such as a lumbar puncture, recent surgery, overshunting, or trauma. Spontaneous intracranial hypotension (SIH) was first described by Georg Schaltenbrand in 1938 and has been recognized as a rare but significantly underdiagnosed differential consideration…

Hemangioblastoma

Background Hemangioblastoma is a vascular tumor of the central nervous system (CNS). It most commonly occurs within or on the surface of the cerebellum and represents the most common primary tumor of the posterior fossa in adults. Hemangioblastomas may also occur within the spine. Single tumors may be sporadic, but multiple tumors are almost always associated with von Hippel-Lindau (VHL) disease. Sporadic tumors appear in the…

Treated Gliomas

Introduction Due to the wide array of available accepted therapies, as well as the increasing number of experimental treatments undergoing clinical trials for the management of glial neoplasms, the task of the radiologist to make appropriate interpretations can seem daunting. In this chapter, we review the clinical, pathologic, and imaging findings associated with these therapies and offer recommendations on the imaging approach in these scenarios. Surgical…

Neurosarcoidosis

Introduction Sarcoidosis is a chronic idiopathic, noninfectious, granulomatous disease characterized by the formation of noncaseating granulomas. It most commonly involves the lungs, skin, and lymph nodes, although any organ or organ system may be affected. The disease most commonly affects African Americans and persons of Scandinavian descent and has a slight female predilection. There is a bimodal age distribution with the initial peak in the third…

Central Nervous System–Immune Reconstitution Inflammatory Syndrome

Introduction Central nervous system–immune reconstitution inflammatory syndrome (CNS-IRIS) represents a diverse group of disorders, all of which are characterized by an exaggerated inflammatory response to either a dead or dying opportunistic infection, viable pathogen from a persistent infection, or a self-antigen. First described in 1992 and most commonly seen in patients with HIV immunosuppression, CNS-IRIS has also been reported in patients following discontinuation of corticosteroids, anti-TNF-α…

Progressive Multifocal Leukoencephalopathy

Introduction Progressive multifocal leukoencephalopathy (PML) is an opportunistic subacute demyelinating infection of the central nervous system (CNS) first described in 1958. The causative agent is the polyomavirus JC that has tropism for oligodendrocytes. Asymptomatic primary infection occurs in childhood, with the virus remaining latent in the kidneys and lymphoid tissue. With profound cellular immunosuppression, the virus reactivates and spreads to the CNS. Presenting symptoms from most…

Autoimmune Encephalitis

Introduction Autoimmune encephalitis refers to a recently recognized group of immune-mediated disorders that involve the central nervous system (CNS). These conditions, which overlap in their clinical manifestations and imaging findings, are ultimately tied to specific antibodies ( Fig. 11.1 ). The clinical and imaging features depend on the particular CNS structure(s) targeted by the antibodies. In addition to limbic encephalitis, which may be the most common…

Acute Disseminated Encephalomyelitis

Introduction Acute disseminated encephalomyelitis (ADEM) is a rare, usually monophasic, immunologically mediated inflammatory disease of the central nervous system (CNS) with characteristic polyfocal involvement of the neuroaxis on imaging. It may occur at any age but is most commonly seen in the pediatric population, with the mean age at presentation between 5 and 8 years. It has a reported incidence of 0.007 to 0.64 per 100,000…

Neurocysticercosis

Introduction Cysticercosis is a parasitic infection caused by the larval stage of the tapeworm Taenia solium . The central nervous system (CNS), eyes, and muscles are the most commonly involved sites. Neurocysticercosis (NCC) is considered the most common parasitic infection of the CNS and is a major cause of acquired epilepsy in some areas of the world. It is reported to affect 50 million people, with…

Toxoplasmosis

Introduction Central nervous system (CNS) toxoplasmosis is an opportunistic infection caused by the intracellular protozoan parasite Toxoplasma gondii . This parasite may be acquired in utero or through the ingestion of infected meat or cat feces, as cats are its definitive host. While T. gondii infects a large portion of the population, it uncommonly causes significant disease in immunocompetent individuals. T. gondii typically causes disease in…

Herpes Simplex Encephalitis

Introduction Herpes simplex encephalitis (HSE) is the most common cause of fatal sporadic encephalitis worldwide. In adults and older children, most cases of HSE are caused by the herpes simplex virus 1 (HSV-1) virus. Patients initially present with nonspecific neurologic signs, including altered mental status, focal cranial nerve defects, hemiparesis, dysphagia, aphasia, ataxia, and seizures, usually with accompanying fevers. Symptoms of encephalopathy then progress with devastating…

Central Pontine Myelinolysis

Introduction Central pontine myelinolysis (CPM) was originally described by . He first detailed the entity in a group of malnourished and alcoholic patients. Further studies and advancement in medicine have shown that CPM most commonly results from the rapid correction of serum sodium in hyponatremic patients. The pathophysiology of CPM is currently not fully understood. However, it has been shown that CPM results from the physiologic…

Wernicke Encephalopathy

Introduction Wernicke encephalopathy (WE) was first described in 1881 by Carl Wernicke as a “superior acute hemorrhagic polioencephalitis.” WE is now recognized as a complication of thiamine (vitamin B1) deficiency and results in the following clinical triad: mental confusion, gait ataxia, and ocular dysfunction. Diagnosing WE is straightforward when a known alcoholic demonstrates all of these symptoms. Unfortunately, this occurs in a minority of patients. One…

Cerebral Amyloid Angiopathy

Introduction Cerebral amyloid angiopathy (CAA) is a microangiopathy defined by progressive deposition of beta amyloid (Aβ) in the walls of distal cortical and leptomeningeal vessels. The resulting small vessel damage can result in hemorrhage, infarction, and/or chronic hypoperfusion, the sequela of which produce a spectrum of characteristic neuroimaging findings. Although both hereditary and sporadic forms exist, in this chapter, we will focus on sporadic CAA, which…

Posterior Reversible Encephalopathy Syndrome

Introduction Posterior reversible encephalopathy syndrome (PRES) refers to a potentially reversible neurotoxic state occurring in association with vasogenic cerebral edema. Although the reported age range varies between 4 and 90 years, most affected patients are in their fourth or fifth decade of life. There is a female predominance, partly attributed to the underlying etiology. Clinically, PRES can present with a constellation of symptoms, with altered mental…

Subdural Hemorrhage and Posttraumatic Hygroma

Introduction The accurate age determination of a subdural hemorrhage is one of the most common and basic assessments in the setting of head trauma. On computed tomography (CT), the classic descriptions of blood products within the subdural space relate to density changes which evolve over time. These changes reflect the evolution from acute blood to clot formation, clot retraction, clot lysis, and eventual resorption. Based on…

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