Corticobasal degeneration is a rare neurodegenerative disease that affects both the cerebral cortex and the basal ganglia. The onset of symptoms of CBD typically occurs between the ages of 50 and 70 years, and the average duration of the disease is six years. It presents with significant motor and cognitive impairments, and is classified as one of the Parkinson-plus syndromes. The disease is difficult to diagnose, as its symptoms are similar to those of other disorders, such as Parkinson's disease, progressive supranuclear palsy, and Lewy body disease, and a definitive diagnosis is only made after neuropathological testing. Because CBD is a progressive disease, a standard set of diagnostic criteria can be used that center on the progression of the disease. These core features include problems with cortical processing, basal ganglia dysfunction, and a sudden and devastating onset of symptoms. Cognitive and psychiatric dysfunction, while present in CBD, are less common and lack sufficient evidence to be considered a common marker of the disease. Although corticobasal degeneration is characterized by a wide range of symptoms, they vary in prevalence. In a study of 147 people with CBD, all patients had at least one parkinsonian sign, 95% had two, and 93% showed some higher level of dysfunction. In a separate study of 14 patients, recorded 3 years after symptom onset, many patients had a wide range of motor symptoms. Seventy-one percent had bradykinesia, 64% had apraxia, and 43% reported limb dystonia, although 36% of cognitive impairment patients had dementia. In another study of 36 patients, half had an alien arm and 27% had gait abnormalities. Here we can see why CBD is so difficult to diagnose. While it is possible to distinguish the disease as a distinct form from other similar diseases, its different symptom clusters create a difficult diagnostic trajectory. Some of the most common symptoms in patients with CBD are specific movement disorders and problems with cortical processing. These symptoms are the first signs of the disease. Each of these associated motor complications appears asymmetrically, with symptoms not being uniform across the body. For example, a person with alien hand syndrome in one hand may not have symmetrical symptoms in the other hand. Notable movement disorders and cortical dysfunctions associated with CBD include: The presence of parkinsonism as a clinical symptom of CBD creates a number of complications that prevent the development of unique diagnostic criteria for the disease. Other diseases in which parkinsonism is a fully diagnostic feature include Parkinson's disease and progressive supranuclear palsy. Parkinsonism in CBD is largely localized to the extremities, such as the arm, and is often characterized by asymmetry. It has been suggested that it most often occurs in the nondominant hand. The most common motor dysfunctions associated with parkinsonism include rigidity, bradykinesia, and gait disturbance, with limb rigidity being the most typical parkinsonian manifestation in CBD. Although relatively subtle, rigidity sometimes leads to disturbances in gait and coherent movements. Bradykinesia in CBD is characterized by a marked slowing of specific limb movements. In a companion study, 71% of patients with CBD showed bradykinesia three years after their initial diagnosis. Alien hand syndrome has been shown to be prevalent in approximately 60% of patients diagnosed with CBD. This disorder involves a person’s failure to control their hand movements, due to the sensation that their limb is “alien.” Alien limb movements are a response to external stimuli and cannot occur in isolation or without stimulation. The alien limb is characterized by its characteristic appearance in CBD, with the patient displaying a persistent tactile stalking sign. This “mitgehen” is a relative feature of CBD, where the patient’s hand seeks to catch up with the examiner’s hand when both hands are in direct contact. A rarer form of alien hand syndrome has been observed in CBD, where the person’s hand displays an avoidance response to external stimuli. In addition, sensory impairment, manifested by numbness or tingling sensations in the extremities, may occur concomitantly with alien hand syndrome, both of which are considered evidence of cortical dysfunction. Alien hand syndrome, like most motor disorders, occurs asymmetrically in those diagnosed with corticobasal degeneration. IMA, although clearly present in CBD, is often atypical, due to the slowness of movement and rigidity associated with these disorders. IMA symptoms in CBD are characterized by the inability to repeat or mimic certain movements with or without achieving goals. This type of IMA is most prevalent in the hands and arms, while IMA in the lower extremities causes gait disturbances. CBD patients who present with IMA symptoms have difficulty initiating walking, with the feet appearing to be planted on the ground. This can lead to stumbling and difficulty maintaining balance. IMA is associated with deterioration in the premotor cortex, parietal association areas, white matter association tracts, thalamus and basal ganglia. Some CBD patients have limb movement apraxia, which manifests as dysfunction in fine movements, mostly performed by the hands and fingers.