BASAL GANGLIA DISEASES;
BG is Planning Centre as it makes plan for any motor activity. This is mediated by dopamine & acetylcholine.
Then the plan is given to Motor Cortex for Execution (Implementation).
So if BG is slow to plan due to lack of dopamine then movements will be slow to initiate ( Bradykinesia). This is the basis of Parkinson’s.
If BG is making abnormal planning under the affect of increased dopamine then movements will be abnormal & rapid. This is what happens in involuntary movements like Chorea, Athetosis, akathisia, dyskinesia, dystonia ,hemibalismus etc
Second role of BG is to support antigravity muscles of the central body to maintain the posture, so postural instability is also a feature of BG disease.
Associated movements like gestures while talking, facial expressions while communicating with others, arm swings during walking are also role of normal BG. So loss of these associated movements is also a feature of BG disease.
Normal BG suppress muscle tone in antagonistic muscles, so that agonists can work smoothly. Loss of this role makes antagonists to oppose all the movements this creating rigidity . alternating increase tone of agonist/antagonist tones leads to resting tremors.
So features of PD ( lack of dopamine activity in Substantial Nigra of midbrain , a part of BG) are
Bradykinesia ( slow to initiate the movements)
Rigidity of antagonistic muscles ( Persistent or Lead pipe usually, but can be interrupted or Cog-wheel if interrupted by tremors ). Rigidity of tongue & speech muscles will cause dysarthria/spastic speech. Rigidity of para spinal muscles will cause flexed posture &/or falls. Rigidity of hand muscles will cause micrographia etc.
Loss of associated movements like facial expressions, arm swings etc.
Resting tremors etc.
Parkinson’s Syndromes which may present as Parkinson’s to start with but don’t respond to dopamine replacement.
- Progressive supra nuclear Palsy: PD+ vertical gaze palsy +spastic limbs & cranial nerve weakness
- Shy Dragger : PD+ autonomic failure in the very early stage of PD due to atrophy of symspthetic neurons in thoracic cord.
- Multisystem Atrophy or Olivo-Ponto-Cerebellar Degenration (MSA/OPCD): PD+ cerebellar signs
- Nigrostriatal Drgenration ( NSD): PD but not responding to dopamine replacement due to loss of striatum as well.
Early dementia, early autonomic failure, cerebellar signs, vertical gaze palsy, autonomic signs like postural hypotension or lack of response to dopamine in the start indicates Parkinson’s syndrome.
As Parkinson’s is disease of substantia Nigra of midbrain, MRI may show MB atrophy.
Degenerative, traumatic, dopamine blocking drugs, ischaemia, SOL are common causes of Parkinson’s.
Chorea; is rapid brake dance like movements , jumping from one joint to the other,mostly at proximal joints of the limbs.
Dyskinesia is almost similar to chorea but due to dopaminergic drugs
Athetosis: is slow writhing movements at distal joints.
Ballismus is a rapid kicking movements , so sudden gross jerks / flail movements.
Dystonia : abnormal sustained contractions with abnormal posturing lasting for sometime mostly minutes.