Lyrics · 完整歌詞
Within the classical model of basal ganglia function,
the direct pathway facilitates movement
while the indirect pathway restrains competing motor activity.
Dopamine from the midbrain dopaminergic nucleus excites D1 receptors on the direct pathway
and inhibits D2 receptors on the indirect one.
When these neurons degenerate, the accelerator weakens and the brake tightens,
yielding bradykinesia, cogwheel rigidity and pill-rolling rest tremor,
with Lewy bodies of alpha-synuclein as the pathological signature.
The receptor
and the rhythm of stimulation decide the side effects of treatment.
Levodopa, given with carbidopa to block peripheral decarboxylation,
is the most effective drug,
yet its short half-life stimulates the striatum in pulses,
and over years wearing-off and dyskinesia emerge.
Agonists such as pramipexole act longer and cause less dyskinesia,
but they stimulate D3 receptors in the mesolimbic reward pathway,
provoking impulse-control disorders, hallucinations, somnolence and oedema.
Entacapone prolongs each dose by inhibiting COMT,
and any D2 antagonist such as haloperidol worsens the parkinsonism.
Within the classical model of basal ganglia function,
the direct pathway facilitates movement
while the indirect pathway restrains competing motor activity.
Site and tremor type place the other movement disorders.
Carbon monoxide destroys the hypoxia-sensitive globus pallidus rather than the midbrain dopaminergic nucleus,
and delayed parkinsonism follows.
Huntington's disease, a CAG repeat disorder with caudate atrophy,
produces early chorea that recedes late as dystonia and akinesia replace it.
Wilson's disease is suspected under forty when tremor
or parkinsonism accompanies liver disease or psychiatric change,
and a Kayser-Fleischer ring, low caeruloplasmin and high urinary copper confirm it.
Headache assessment begins by excluding a secondary cause,
and every SNOOP flag has a mechanism.
Systemic features suggest infection or vasculitis; deficits or papilloedema suggest a mass.
A thunderclap onset means a ruptured vessel until subarachnoid haemorrhage is excluded.
New headache after fifty raises giant cell arteritis,
which demands corticosteroids before biopsy.
Orthostatic headache with diffuse dural enhancement is intracranial hypotension,
whereas an obese young woman with papilloedema
and a raised opening pressure has idiopathic intracranial hypertension.
Among primary headaches, migraine arises from trigeminovascular activation with CGRP release,
and its aura is cortical spreading depression;
cluster headache follows the hypothalamic clock and the trigeminal autonomic reflex.
Triptans, agonists at 5-HT1B and 5-HT1D receptors,
constrict meningeal vessels and suppress CGRP release,
but coronary disease and uncontrolled hypertension forbid them.
Cluster attacks respond to high-flow oxygen and verapamil prevents them,
whereas migraine prevention uses propranolol, topiramate, valproate or amitriptyline, never carbamazepine,
which belongs to trigeminal neuralgia.
A tumour announces itself through raised pressure from its mass,
deficits from local destruction and seizures from cortical irritation.
Growth rate decides which comes first,
so slow low-grade gliomas present with seizures more often than glioblastoma,
which destroys and compresses.
Meningioma,
arising from arachnoid cap cells outside the brain with a dural tail,
is the commonest primary intracranial tumour.
Vestibular schwannoma grows from the vestibular nerve;
bilateral tumours define neurofibromatosis type 2,
and surgery most often injures the facial nerve.
Within the classical model of basal ganglia function,
the direct pathway facilitates movement
while the indirect pathway restrains competing motor activity.