Cortical-basal Syndrome is a term encompassing
several possible conditions presenting with a combination of similar clinical signs and symptoms. The distinctive features are an asymmetric levodopa-resistant (poor response to medication for
Parkinson's disease), akinetic-rigid (slowness and stiffness) syndrome associated with "cortical" features such as apraxia (the loss of the ability to make specific movements despite preserved power), cortical sensory loss (discrimination of different sensory testing including naming objects placed in the hand or numbers written in the
hand), and alien limb (an arm behaving as if it has a mind of it's own) phenomenon. Cognitive dysfunction (memory, complex task completion) is now considered a common associated feature.
The common possible causes of this syndrome include:
Cortical basal degeneration typically begins from 50 – 70 years of age. Mean survival is about 8 years.
Parkinsonian signs including unilateral
limb rigidity (79%), bradykinesia (71%), postural instability (45%) and apraxia are found in almost all patients. Dystonic posturing of the arm and hand is common (43%). Tremor when present is typically
an action tremor that improves at rest. It frequently has a myoclonic (jerky) component. Stimulus sensitive myoclonus can be seen. The rigidity may be extreme and associated pain is common.
With progression cortical sensory
deficits, pyramidal tract dysfunction, dysarthria, dysphagia and other symptoms emerge or worsen. Alien limb phenomena develop in 50% of cases. It may be as simple as levitation of a limb. Magnetic
apraxia (approach behavior with groping and manipulation) is a sign of CBGD. Described eye movement abnormalities include saccadic pursuit, difficulty initiating saccades, and rarely supranuclear palsy.
CBGD, like PSP is a disorder of the tau
protein (a tauopathy). It has significant overlap with the frontotemporal dementias (FTD), parkinsonism associated with chromosome 17 (FTDP-17), primary progressive aphasia (PPA), Pick's disease, and PSP.