Organic versus Functional causes for abnormal mental state

Evaluation of the patient with altered behaviour and / or thought processes requires an organised and systematic approach so that life threatening medical emergencies either coexisting with or causative of the ‘psychiatric’ symptoms are identified and managed. Studies have documented that clinicians frequently overlook coexistent medical disease in patients who present with apparent psychiatric conditions. Common conditions that are missed include toxicity due to alcohol or illicit drug use, alcohol withdrawal, self poisoning and iatrogenesis secondary to prescribed drug use. Where an organic disease process is responsible for the altered behaviour / thought process, the syndrome is known as an Organic Brain Syndrome

The causal relationship between organic disease and psychiatric symptoms is also well established. In a recent study of 100 patients aged 16 to 65 years presenting with new psychiatric symptoms who were extensively investigated in the Emergency department, 63 were found to have an organic aetiology for their symptoms. (Henneman et al, Ann Emerg Med 1994 Oct; 24 (4):672-7).

ORGANIC BRAIN SYNDROME : DIFFERENTIAL DIAGNOSIS

A wide variety of medical conditions may cause psychiatric symptoms (altered behaviour and thought processes). They can, however, be divided into two main categories :

1. Toxic / Metabolic processes eg Infections, Toxins, Electrolyte / Metabolic disorders

2. Organic CNS disease eg Seizures, Tumours, Vascular lesions, Trauma, Infection

The table below summarises the causes that need consideration in a patient with organic brain syndrome.

1. Toxic / Metabolic

• Infection Urinary Tract, Lung, Skin
• Toxic Poisoning, Alcohol/Drug Abuse and Withdrawal
• Metabolic / Elecs Liver/Renal failure, Diabetes, Sodium/Calcium disturbances
• Cardio/Resp Hypoxia, Hypercarbia, Hypertension, Hypotension

2. Primary CNS Disease

• Seizures Status Epilepticus, Postictal
• Brain Tumour
• Vascular Intracerebral Haemorrhage, SAH, CVA
• Trauma Concussion, Contusion, Haematoma
• Infection Meningitis, Encephalitis, Abscess

In a study by Purdle et al (Ann Emerg Med 10:455-460, 1981) of 100 patients with organic brain syndrome presenting to the Emergency department the three leading causes for organic brain syndrome were

• Toxic Ingestion (28%),
• Infection (13%)
• Fluid / Electrolyte Imbalances (12%)

DIFFERENTIATING ORGANIC FROM PSYCHIATRIC

A high degree of suspicion for the presence of medical disease is required in all patients presenting to the Emergency Department. However, differentiating an organic from a functional (or psychiatric) cause for the patient with altered behaviour or thought process can be an extremely difficult task. Henneman, in the study quoted above, concluded that most alert adult patients with new psychiatric symptoms have an organic aetiology and recommended performing a medical history, physical examination, laboratory investigations (EUC, BSL, Calcium, CK, Alcohol and drugs screens), CT scan and Lumbar puncture as part of the medical clearance of these patients. The following paper outlines a useful approach to this problem and highlights the risk factors for identifying patients most likely to have an organic basis for their symptoms.

All patients presenting with altered behaviour or altered thought processes (eg hallucinations, delerium) should first be assumed to have an organic cause for their symptoms until this has been specifically ruled out. Features recognised as useful clues to the presence of underlying organic disease in a patient with psychiatric symptoms include the following:

1. Clouding of Consciousness

2. Altered Cognition (Disorientation, Memory Disturbances, Poor Serial 7’s)

3. Abnormal Vital signs

4. Age > 40 years. No past psychiatric history.

Other clues from the history and examination that suggest a organic aetiology include: the acute onset of symptoms, the presence of visual or tactile hallucinations, severe headache / vomiting, a recent history of surgery or hospitalisation, use of prescribed medications, substance abuse, seizures and incontinence. These are summarised in the table below.

Table 1 : Features favouring psychiatric versus organic causes for abnormal behaviour

MANAGEMENT PROTOCOL

To assist in ruling out organic processes the following protocol has been instituted at the Lyell McEwin. In all patients who present with psychiatric symptoms (ie for psychiatric assessment) the following must be completed before a psychiatric diagnosis is made or a psychiatric opinion sought.

Nursing assessment

• Vital signs
• Blood glucose level, oximetry and urine analysis
• Neurological observations (Glasgow coma score, pupils)

Medical assessment

• Assess history for risk factors suggestive of organic brain syndrome (Table 1)
• Check above observations (and ensure they are complete)
• Cognition : Assess orientation, short and long term memory, serial 7s
• Focal neurological examination : Assess pupils, nystagmus, extraoccular movements, limb tone, DTRs, coordination
• Assess chest (for pneumonia), abdomen (acute abdomen). Exclude meningism (SAH)

Nb. Where there is a history (or suspicion) of recent alcohol or illicit drug use a minimental examination must be performed. (a score of > 23 will imply no further evaluation and no blood alcohol level is required)

OUTCOME

Patient is cleared

If the history is not suggestive of an organic cause (see table 1) and all of the above examination findings are unremarkable the patient can be medically cleared for psychiatric review. The medical registrar is not required to assess the patient. It is important that the form for the "Medical Clearance for patients presenting with psychiatric symptoms" is completed (and signed) and a copy given to the psychiatric team who arrive to assess the patient.

Patient is not cleared

In patients with a history suggestive of an organic cause (table 1), are a high risk group (eg the elderly, complex medical / drug history) or have abnormal examination findings, the following investigations should always be performed : ABG’s, EUC and Calcium, CBP, Alcohol level, ECG and CXR. CT scan of the head is generally indicated only if there is evidence of raised intracranial pressure, focal neurological findings, impaired conscious level, recent history of head trauma, meningism.

If not already, the patient must then be assessed by either an ED senior medical officer or where admission is likely the medical registrar.

GUIDELINES FOR ADMISSION

Where organic disease is suspected or confirmed as a cause of the patient’s symptoms they must be managed on a medical unit until the medical condition has either resolved or has been appropriately treated. Particular life threatening conditions that must always be excluded include drug poisoning / withdrawal, sepsis, diabetic emergencies and SDH / SAH. Where necessary psychiatric review can be arranged with the psychiatric liason service (weekdays) or through ACIS (weekends) on the following day.

There is no doubt that the concurrent presence of a medical condition such as alcohol or drug poisoning or infection will make the accurate psychiatric assessment of a patient impossible whether or not it is determined to be the cause of the psychiatric symptoms. It is best to view the presence of a medical condition as masking any underlying psychiatric condition and begin by correcting the organic cause first (by admission to hospital). Once this corrected a psychiatric opinion can be sought to establish the presence of psychiatric illness.