Secondary parkinsonism can be caused by a cavernoma — a cluster of abnormal blood vessels — located in a brain region involved in voluntary movement control, a case report shows.
The case-study, ”Nine-years follow-up of cavernoma located in basal ganglia mimicking Parkinson’s disease,” was published in the journal Clinical Neurology and Neurosurgery.
Most patients (about 80–85%) diagnosed with Parkinson’s disease have what is called primary parkinsonism or idiopathic Parkinson’s disease (meaning the disease has no known cause). This type tends to respond well to therapies that work by increasing or substituting dopamine molecules in the brain.
The remaining types of Parkinson’s are known as secondary parkinsonism. In these cases, the cause of the disease is often known, but patients fail to respond well to dopaminergic medications intended to replace dopamine or prevent its degradation, such as levodopa.
Secondary parkinsonism can be caused by a variety of factors. In rare cases, it is caused by cavernoma, a cluster of abnormal blood vessels in the basal ganglia (a brain region often affected in Parkinson’s). This occurs in only 0.46% of the general older population, and in 0.037% of older individuals with Parkinson’s symptoms, according to the report.
In this study, researchers cite the case of a 75-year-old woman with secondary parkinsonism due to a cavernoma in the right striatum — a brain region involved in voluntary movement control — and one of the major components of the basal ganglia.
In 2009, the patient was diagnosed with Parkinson’s after clinical examination by a neurologist. Her symptoms included bradykinesia (slowness of movement) and rigidity of her left limbs, cogwheel phenomenon (a type of rigidity common in Parkinson’s) of the right upper-limb that occured upon contralateral (opposite) hand activation, and an unsteady gait.
“The patient referred to a loss of interest in her hobbies in the preceding years and difficulties in initiating speech and movement,” the researchers wrote.
The neurologist, suspecting Parkinson’s disease, recommended brain magnetic resonance imaging (MRI), a Dopamine Transporter Single Photon Emission Computerized Tomography (DaTscan), and an olfactory (smell) test.
DaTscan is a tool used to confirm the diagnosis of Parkinson’s disease. It is a specific type of single-photon emission computed tomography (SPECT) imaging technique that helps visualize dopamine transporter levels in the brain. In Parkinson’s, there is a steady loss of dopamine transporters (DaT) in the brain. These mediate the flow of the neurotransmitter dopamine between nerve cells.
The results revealed severely decreased dopamine transporter uptake in the right striatum. The brain MRI scan showed that the patient had a 2-centimeter cavernoma in the basal ganglia, as well as small vessel disease (microangiopathy), which also was detected in the brain’s white matter.
The olfactory test showed no impairment in her ability to smell or to detect odors (a condition called hyposmia).
As a result, the patient, who never had received medication that could have caused secondary parkinsonism, was given low-dose levodopa.
Over a nine-year period, however, her left kimb parkinsonism did not appear to progress. The patient never experienced rest tremor, motor fluctuations or dyskinesia (involuntary muscle movement) typical of Parkinson’s. Only the patient’s apathy and gait unsteadiness appeared to deteriorate. Furthermore, the patient stated that she did not respond to levodopa treatment, even following a dose increase to 750 mg/day.
As a result, neurologists re-evaluated her diagnosis. They performed the levodopa test and the apomorphin-challenge-test, both used to determine whether motor symptoms such as tremors in the limbs, rigidity in the muscles, and problems with walking, balance and fine motor coordination, are caused by Parkinson’s.
The tests consist of giving levopoda or apomorphine (brand name Apokyn) to understand if these Parkinson’s-specific treatments improve patients’ symptoms. If it does, the patient likely has Parkinson’s.
The results for both tests were negative. Brain MRI showed that the cavernoma had increased slightly in size. Another DaTscan showed that the dopamine transporter uptake had undergone a mild-to-moderate worsening compared to the first assessment.
One week after progressively discontinuing levopoda treatment altogether, the patient showed no worsening of her symptoms.
Based on all these observations, the patient was diagnosed with secondary parkinsonism caused by cavernoma. “We conclude that a cavernoma in the striatum can cause secondary parkinsonism and apathy mimicking PD at the first neurological assessment,” the researchers wrote.
Unlike Parkinson’s, secondary parkinsonism caused by cavernoma can remain unchanged over many years, and lead to the drop of dopamine receptors detected in the DaTscan.