Progressive Supranuclear Palsy (PSP)

Progressive supranuclear palsy (PSP) is an idiopathic rare degenerative disease of the brain. Many people with PSP experience changes in mood, behavior, and personality. A decline in thinking, memory, attention, and speech, is not uncommon. Symptoms typically become noticeable in the early 60s, although the disease sometimes affects people in their 40s or 50s. PSP is slightly more common in men than in women.The pattern of symptoms varies widely from person to another. Often, friends and family members are more aware of these changes than the affected person.

Ocular manifestations of PSP

The frontal lobe and the parietal lobe are responsible for generating horizontal eye movements, while vertical eye movements are generated from the midbrain.The final pathways for eye movements are the nuclei of the 3rd, 4th and the 6th cranial nerves in the brainstem.

Supranuclear gaze palsies result from interruption of the neural pathways that carry commands for voluntary eye movements before they reach the eye movement “generators” in the brainstem.

Loss of voluntary eye movements results from interruption of neural pathways that carry commands from the cerebral cortex to the ocular motor nuclei in the brainstem is called supranuclear palsy, in this condition the invoulantary eye movements are not affected. On the other hand, in nuclear or infranuclear palsy where the nuclei of the cranial nerves or the peripheral cranial nerves are affected, all types of eye movements are lost whether voluntary or involuntary. 

 We can say that voluntary eye movements are lost in gaze palsy whether it is of supranuclear or infranuclear origin. While involuntary eye movements are intact in supranuclear palsy, but they are lost in nuclear and infranuclear palsy.

Differentiating Supranuclear from Nuclear and Infranuclear Lesions gaze palsies ( like chronic progressive external ophthalmoplegia ) is based on the presence or absence of involuntary eye movements ( Reflex eye movements ), the clinician should determine whether the eyes can be moved reflexively in the direction of the “paralysis” by testing the oculocephalic (Doll’s eyes) or not. In Supranuclear gaze palsy the reflexes are intact ( oculocephalic, vestibulocular and bell's phenomenon ), while in nuclear or infranuclear gaze palsy, these reflexes are lost.

The etiology of PSP is unknown. Pathologically, the disease is characterized by neurodegeneration, gliosis, and abnormal accumulation of tau protein in the basal ganglia, brain stem, prefrontal cortex, and cerebellum.

The diagnosis of PSP is exclusively clinical; laboratory tests and imaging exams cannot detect the disease, but help rule out other pathologies.

To date, there is no effective medication or surgical treatment to cure or delay the progression of the symptoms in PSP, no drug has been found to efficiently treat the origin of the problem.