Increased intracranial pressure (ICP): Pseudotumor cerebri
Vascular:  Stroke, subarachnoid hemorrhage, aneurysm (extremely rare), microvasculopathy from diabetes, atherosclerosis or hypertension
Neoplastic: Tumor in the subarachnoid space
Degenerative/deficiency: Vitamin B12 deficiency, Wernicke-Korsakoff syndrome
Idiopathic: Most common cause of acquired trochlear nerve<unk> .
Infection: Meningitis, herpes zoster
Congenital: Dysgenesis of trochlear nerve nucleus or abnormal peripheral nerve
Autoimmune: Myasthenia gravis, multiple sclerosis, systemic lupus erythematosus, giant cell arteritis, Sjögren
Trauma: Its long course makes it susceptible to traumatic injury. Head trauma (adult) is the second most common cause. Is generally severe with loss of consciousness. Consider underlying structural abnormalities if results after minor trauma.
Endocrine: Thyroid ophthalmopathy  
Third nerve<unk> 
Abducens nerve<unk>
Fourth nerve palsy
Increased intracranial pressure 
Third nerve palsy
Vascular:  Stroke, subarachnoid hemorrhage, aneurysm 
Sixth nerve palsy
Neoplastic: Tumor in the subarachnoid space
Ulnar neuropathy
Degenerative/deficiency: Vitamin B12 deficiency, Wernicke-Korsakoff syndrome