Corticobasal degeneration is a pathologic entity. Presenting clinical phenotypes include corticobasal syndrome (CBS), frontal behavioral spatial syndrome, aphasia, progressive supranuclear palsy-like syndrome (PSPS), and a predominantly cognitive phenotype often mistaken for Alzheimer’s disease (AD). Treatment of CBD is symptomatic, particularly given recently negative neuroprotective studies. Given the relentless progression in CBD, all interested patients should be offered the opportunity to enroll in clinical neuroprotective trials as they arise. For symptomatic therapy, treatment options are necessarily based on evidence from other disorders given the lack of studies in CBD. In patients with CBS and PSPS, parkinsonism is treated with levodopa/carbidopa. This generally has modest and transient benefits at best and often results in no improvement. Botulinum toxin injections are the treatment of choice for limb dystonia. Clonazepam and levetiracetam are commonly used for myoclonus. Physical therapy is an important part of motor treatment, particularly for fall prevention strategies and assist device assessment. Whether medications such as cholinesterase inhibitors or memantine have any role in CBD is unclear given the various responses described in related phenotypes and diseases. Treating the behavioral symptoms associated with CBD is critical in an attempt to treat symptoms for which we have good pharmacologic interventions and to hopefully improve quality of life. General supportive care is important, including assessing for sores related to dystonia or immobility, monitoring dysphagia, and identifying needs for support services. Finally, as with other relentlessly progressive neurodegenerative diseases, it is critical to provide family and caregiver support and to assess for when palliative care services will serve the patient best.
Square wave jerks. This patient had no ability to converge.
Testing — especially eye movement
There is still gain at the "turnaround point, but then the eye goes "flat line" as it runs into the orbit. Similar "hang ups" can be seen in other supranuclear eye movement disorders, including SCA7. At the bedside, this can be seen by having the patient attempt to suppress their VOR, elicited by sinusoidal movement of the head at about 1 hz, while looking at a fixation target within the goggle. Horizontally there are fast phases. Vertically, the eye goes up and down with the goggles. In our opinion, the oculomotor findings of CGBD are identical to those of PSP.
We are interested in CGBD because it is associated with slowing of eye movements.
Corticobasal ganglionic degeneration, also known as Corticobasal degeneration or corticobasal syndrome (CBS). We will call it CBGD. CBGD is a rare progressive neurological disorder characterized by a combination of Parkinsonism and cortical dysfunction. It is a rare sporadic progressive disorder first reported in 1968. CBGD appears to be VERY closely related to another, less rare, sporadic neurodegenerative disorder named Progresive Supranuclear Palsy (PSP) . In CBGD, cognitive symptoms dominate, while in PSP, eye movement symptoms dominate the picture. However they often share the same genetics, so they are probably just the same disease, seen through the eyes of different neurology subspecialties. The parkinsonism of CBGD is generally an asymetric akinetic rigid syndrome, unresponsive to levodopa, similar to that of multiple system atrophy and PSP. Eye movement abnormalities are common, as in PSP, and a supranuclear gaze palsy can be seen as in PSP. Given the pathologic similarities between CBGD and PSP, it seems probable that they are simply two "faces" of the same disease, perhaps mixed in with other obscure neurological conditions that can by chance, cause a similar constellation of findings. The internet has enabled easier case finding. The Armstrong criteria (2013) outlined syndromes of CGBD, associated with the pathology. These can be found online: “https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3590050/ . They provide features of 5 phenotypes of CGBD, including "probable", "possible", frontal behavioral-spatial syndrome, a variant of primary progressive aphasia, and a variant resembling PSP. They also outlined diagnostic criteria, which included the "syndromes" noted above. There is certainly overlap here with PSP.