Corticobasal degeneration (CBD) is a neurodegenerative disorder that has gained interest of neurologists, neuropathologists, and other neuroscientists in the last four to five decades. Over the past years, there has been a tendency to consider CBD as a syndrome more than a nosologic entity because of the heterogeneity of clinical presentations and overlap of the clinical and pathological features with other neurodegenerative diseases. The patients with the classical motor presentation may be still very characteristic, and currently most of the pathologically confirmed cases of CBD can be divided into two distinct groups: (1) patients that present mainly with a movement disorder and (2) patients that develop cognitive problems. As the disease progresses, most of the patients may manifest both types of symptoms. The lack of biomarkers for the diagnosis of the different neurodegenerative processes makes the premortem diagnosis of these disorders even more inaccurate and difficult to differentiate in a clinical setting. CBD was originally called corticodentatonigral degeneration with neuronal achromasia, based in the pathological findings of three original cases described by Rebeiz and colleagues in 1967.1 The term “CBD” was initially used by Gibb and colleagues in 1989,2 and in 2000, the term CBD Syndrome was proposed by Kertesz.3 Other names used to describe the cases of CBD included corticonigral degeneration with neuronal achromasia,4 corticodentatonigral degeneration,5 cortical-basal ganglionic degeneration,6 and myoclonic dystonia.7 In the nineteenth century, Jean-Martin Charcot, Alfred Vulpian, and their disciples described cases of atypical Parkinson's disease (PD) with jerking movements and abnormal posture of the limbs, called originally “hemiplegic parkinsonism.”8,9 Many of these clinical cases lack a complete description, since the characterization of many neurologic signs and symptoms such as apraxia, dystonia, cortical sensory deficits, and myoclonus were not a regular part of the neurological examination performed at that time. The description of some of Charcot's atypical parkinsonian cases has some of the distinctive features that we consider today associated with CBD. Jacques Lhermitte in 1925 described a clinical case to the French Neurological Society that is suggestive of CBD.10 “A 67-year-old carpenter with progressive right hand clumsiness, unable to ambulate independently at age of 72, with the right arm flexed and an involuntary right arm movement ‘like a foreign body,’ unable to recognize objects in his right hand, in spite of normal primary sensation.”
In this chapter, we describe our current understanding of CBD and its place in the spectrum of neurodegenerative disorders. However, before we embark on a formal delineation of current concepts, we will review the original reported cases. Rebeiz and colleagues described three patients in 1967 at the Massachusetts General Hospital with a unique pattern of progressive motor impairment in later mid-life. The clinical symptoms were characterized by slow, awkward involuntary limb movements accompanied by tremor and dystonic posturing. In all three cases, dysfunction began and remained most prominent in the left limbs. Stiffness, slowness, lack of dexterity or clumsiness, and “numbness” or “deadness” were ...