Apallic syndrome – Causes, Diagnosis, and Prognosis.


Apallic syndrome (AS) also called Unresponsive Wakefulness Syndrome (UWS) and Persistant Vegetative State. It is a result of a traumatic brain injury such as diffuse, bilateral cerebral cortical degeneration and anoxia, or encephalitis which causes the brain to halt the ability to create thoughts, experience sensation, and remember past events.

Patients in a vegetative state are awake, but show no signs of awareness. They may be able to open their eyes, have basic reflexes to actions, and wake up or fall asleep at various intervals. UWS patients are also able to breathe without mechanical assistance, while maintaining a regular heartbeat.

The amount of communication and cognitive mechanisms is limited with UWS. Patients might be able to swallow, grunt, smile, or moan without any external stimulus. They are also unable to obey verbal commands. Below figure shows the states of UWS.


Stages of AS


The syndrome was first described in 1940 by Ernst Kretschmer who called it Apallic Syndrome. The term persistent vegetative state was coined in 1972 by Scottish spinal surgeon Bryan Jennett and American neurologist Fred Plum to describe a syndrome that seemed to have been made possible by medicine’s increased capacities to keep patients’ bodies alive.


The overall incidence of new AS/VS full stage cases all etiology is 0.5–2/100.000 population per year. About one third are traumatic and two thirds non traumatic cases. For Europe prevalence of AS in hospital cases is reported to be 0.5–2/100.000 population/ year, about one quarter to one-third secondary to acute traumatic and roughly 70% following acute non-traumatic brain damage and chronic neurological diseases.

Risk factors of apallic syndrome

  • Corpus callosum and dorsolateral brainstem lesions associated with increased risk for nonrecovery in patients with posttraumatic vegetative state.
  • In case of children in coma after acute brain injury, absence of cortical somatosensory evoked potentials may identify patients not likely to awaken.

Signs and symptoms

  • Most PVS patients are unresponsive to external stimuli and their conditions are associated with different levels of consciousness.
  • PVS patients’ eyes might be in a relatively fixed position, or track moving objects, or move in a disconjugate (i.e., completely unsynchronized) manner. They may experience sleep-wake cycles, or be in a state of chronic wakefulness.
  • They may exhibit some behaviors that can be construed as arising from partial consciousness, such as grinding their teeth, swallowing, smiling, shedding tears, grunting, moaning, or screaming without any apparent external stimulus.
  • Individuals in PVS are seldom on any life-sustaining equipment other than a feeding tube because the brainstem, the center of vegetative functions (such as heart rate and rhythm, respiration, and gastrointestinal activity) is relatively intact

Causes of apallic syndrome

There are three main causes of PVS (persistent vegetative state):

  • Acute traumatic brain injury
  • Non-traumatic: neurodegenerative disorder or metabolic disorder of the brain
  • Severe congenital abnormality of the central nervous system

Medical books (such as Lippincott, Williams, and Wilkins. (2007). In a Page: Pediatric Signs and Symptoms) describe several potential causes of PVS, which are as follows:

  • Bacterial, viral, or fungal infection, including meningitis
  • Increased intracranial pressure, such as a tumor or abscess
  • Vascular pressure which causes intracranial hemorrhaging or stroke
  • Hypoxic ischemic injury (hypotension, cardiac arrest, arrhythmia, near-drowning)
  • Toxins such as uremia, ethanol, atropine, opiates, lead, colloidal silver
  • Trauma: Concussion, contusion
  • Seizure, both non convulsive status epilepticus and post convulsive state (postictal state)
  • Electrolyte imbalance, which involves hyponatremia, hypernatremia, hypomagnesemia, hypoglycemia, hyperglycemia, hypercalcemia, and hypocalcemia
  • Post infectious: Acute disseminated encephalomyelitis (ADEM)
  • Endocrine disorders such as adrenal insufficiency and thyroid disorders
  • Degenerative and metabolic diseases including urea cycle disorders, Reye syndrome, and mitochondrial disease
  • Systemic infection and sepsis
  • Hepatic encephalopathy

Diagnosis and testing

Use of functional neuroimaging studies to study implicit cognitive processing in patients with a clinical diagnosis of persistent vegetative state includes the following techniques:

  • Positron emission tomography (PET)
  • Functional magnetic resonance imaging (fMRI),
  • Electrophysiological

Treatment of apallic syndrome

Treatment can’t ensure recovery from a state of impaired consciousness, however supportive treatment is used to give the best chance of natural improvement. This can involve:

  • Providing nutrition through a feeding tube
  • Making sure the person is moved regularly so they don’t develop pressure ulcers
  • Gently exercising their joints to prevent them becoming tight
  • Keeping their skin clean
  • Managing their bowel and bladder – for example, using a catheter to drain the bladder
  • Keeping their teeth and mouth clean
  • Efforts should be made to establish functional communication and environmental interaction when possible. Offering opportunities for periods of meaningful activity – such as listening to music or watching television, being shown pictures or hearing family members talking

Sensory stimulation:

  • Visual – showing photos of friends and family, or a favorite film
  • Hearing – talking or playing a favorite song
  • Smell – putting flowers in the room or spraying a favorite perfume
  • Touch – holding their hand or stroking their skin with different fabrics

Pharmacological therapy mainly uses activating substances such as tricyclic antidepressants or methylphenidate. Mixed results have been reported using dopaminergic drugs such as amantadine and bromocriptine and stimulants such as dextroamphetamine. Surgical methods such as deep brain stimulation are used less frequently due to the invasiveness of the procedures.

Prevention of apallic syndrome

Helmet use may reduce risk of head injury in various risk activists such as follows

  • Bicyclists
  • Motorcycle riders
  • Skiers
  • Snowboarders

Prognosis of apallic syndrome

  • Many patients emerge spontaneously from VS/UWS within a few weeks. Some people improve gradually, whereas others stay in a state of impaired consciousness for years. Many people never recover consciousness.
  • The chances of recovery depend on the extent of injury to the brain and age, with younger patients having a better chance of recovery than older patients. Generally, adults have about a 50 percent chance and children a 60 percent chance of recovering consciousness from VS/UWS within the first 6 months in the case of traumatic brain injury.
  • For non-traumatic injuries such as strokes, the recovery rate falls within the first year. After this period the chances that VS/UWS patient will regain consciousness are very low and, of those patients who do recover consciousness, most experience significant disability.
  • The longer a patient is in VS/UWS the more severe the resulting disabilities are likely to be.
  • Some patients who have entered a vegetative state go on to regain a degree of awareness (see Minimally Conscious State).
  • The likelihood of significant functional improvement for VS/UWS patients diminishes over time.
  • There are only isolated cases of people recovering consciousness after several years.
  • The few people who do regain consciousness after this time often have severe disabilities caused by the damage to their brain.

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