A persistent vegetative state occurs when, after a coma, a patient loses cognition and can only perform certain, involuntary actions on his or her own. While some describe those in a persistent vegetative state as "brain dead," in fact, the lower brain stem in PVS patients is still healthy and fully functioning.

As a result, patients in persistent vegetative states can:

  • blink and otherwise move their eyes
  • breathe on their own
  • cry or laugh, though not as an emotional response to external events
  • enjoy normal circulation
  • experience regular sleep-wake cycles
  • move their limbs, though purely as reflex (PVS patients can't hold their limbs nor move them on command.)
  • open their eyes
  • smile
  • track objects with their eyes

Keep in mind that all of the above responses are largely physical reactions.

Although PVS is associated with varying degrees of consciousness (the strongest in which patients still minimally respond to stimuli), most PVS patients have no perception of and, therefore, no ability to react to external stimuli. For them, any movement or response is purely spontaneous, unpredictable and unconnected to events outside of physical impulse.

Can PVS Patients Talk?

It's important to note that those in persistent vegetative states are unable to speak and, for the most part, unable to respond to vocal commands (Again, those with the strongest degrees of consciousness may be able to respond to minimal stimuli). Instead, they are limited to certain noises, most of which are involuntarily made.

Noises commonly made by patients in persistent vegetative states include:

  • crying
  • grunting
  • laughing
  • moaning
  • screaming

Coma versus PVS

A coma is a condition marked by a profoundly debilitating lack of consciousness. Patients in a coma won't be able to perceive or respond to external stimuli. While those in a coma may make involuntary movements, just as those in a persistent vegetative state can, coma patients have no level of higher consciousness.

Therein lies the difference between a coma and a persistent vegetative state: In PVS, patients may still have low levels of consciousness.

Causes of Persistent Vegetative States

Both head injuries and genetic disorders can cause people to fall into a persistent vegetative state. While a car accident or a concussion can result in head injuries severe enough to trigger PVS, so too can inherited brain and nervous system disorders.

Other possible causes of persistent vegetative states may include:

  • drug abuse
  • high intracranial pressure (ICP)
  • hyperglycemia
  • infections, such as Meningitis
  • ingestion of toxins (such as lead or opiates)
  • seizures
  • stroke
  • thyroid disorders
  • tumors

Persistent Vegetative State Treatment

Currently, no cure exists for "waking" patients from a persistent vegetative state. Instead, medical professionals take efforts to keep the patient healthy and comfortable.

In many instances, patients will wake instantaneously without any warning within the first month of being in a persistent vegetative state. In general, patients have the best odds of emerging from PVS during the first year: While children have 60 percent change of regaining consciousness, adults only have a 50 percent change of recovery.

After one year, it's highly unlikely that patients will emerge from their persistent vegetative state. For those who do, severe disabilities often accompany consciousness.

To aid in emergence and facilitate recovery, different types of rehabilitation are beneficial. The appropriate type of rehabilitation, as well as an individual's chances for recovery, depends on the cause and severity of the persistent vegetative state.