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Central nervous system emergencies 

Central nervous system emergencies

Central nervous system emergencies

Nigel D. Robb

and Jason Leitch

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Subscriber: null; date: 25 February 2017


This chapter will deal with emergencies originating in the central nervous system (CNS). The conditions covered are:

  • Epilepsy

  • Stroke (cerebrovascular accident)

  • Transient ischaemic attack (TIA).


Epilepsy is actually a catch-all term for a number of distinct conditions and syndromes with causes ranging from hereditary to unknown. The definition that is generally recognized is ‘a chronic brain disorder of various aetiologies characterized by recurrent seizures due to excessive discharge of cerebral neurons’. For the dental surgeon, the intricacies of the individual diagnosis are unimportant but the ability to recognize and promptly deal with the seizures is vital. The manifestations of the condition range from short absences, where the patient may appear not to be paying attention, through to ‘grand mal’ fits.


  • Usually known epileptic

  • Varied presentation

  • Simple vacancy, through petit mal, to full grand mal seizure

  • Varied duration.

Immediate management

  • Stop treatment

  • Ensure safety of patient and team

  • Maintain airway

  • Monitor length and strength of seizure

  • Reassure

  • High-flow oxygen via face mask.

Risk factors

  • Usually history of seizures

  • Stress

  • Pain

  • Infection.

Delayed management

  • If prolonged and/or recurring (status epilepticus), seek hospital admission

  • Intranasal midazolam

  • If first seizure, then cause must be investigated.

Diagnosis in the dental surgery

Seizures can occur for a multitude of reasons in the dental surgery. As described in Chapter 3, they can simply be the result of a prolonged faint. Other seizures commonly seen in the dental surgery are usually the result of epilepsy or epileptic syndromes. Patients will usually give a history of seizures in the past.

Patients will often, but not always, report a prodromal phase when they are aware that they are going to seizure. Prompt action at this point may avert injury to the patient and the dental team.

Seizures may be simply evidenced by a short loss of awareness which will be self-limiting. The classic tonic-clonic seizure can be of varied strength and length. The majority will be short and self-limiting.


The best management of seizures in the dental surgery is to prevent the seizure. This is frequently easier to say than to achieve.

Patients often understand their disease very well and respond well to questioning about risk factors. Reduction of anxiety is a key feature of prevention.

Risk assessment

The most important aspect of prevention is once again risk assessment. A thorough medical history is vital and will reveal details of the patient’s epilepsy history which the dental team will need to take into account when assessing the risk of treatment. Factors to note include:

  • Drug therapy—drug type, drug dose, drug frequency, length of use

  • Treating physician—neurologist or a GP?

  • Causes of previous seizures—pain, anxiety, etc.

  • Seizure history—has it been three years or three days since last seizure and seizure type? Is there a prodromal phase? Has there ever been status epilepticus?.

These questions will allow the team to assess how likely a seizure is for this individual patient and to take appropriate measures to limit the risk and be prepared to treat any seizures which may occur.


It is vital to reduce the risk as far as possible. If a patient reports that seizures worsen as a result of anxiety, it may be appropriate to consider some form of anxiety control such as sedation, either inhalation or intravenous.

When considering the use of sedation, it is important to remember that hypoxia is a potential trigger for epileptic fits. When intravenous sedation is used, a wise precaution is the administration of supplemental oxygen via nasal cannulae.

Preventing injury

A rubber mouth prop may be used when treating patients who are prone to fitting. The mouth prop will not prevent the fit occurring, but it will help prevent injury to the dental team as a result of the patient biting during a fit.

Immediate management

The first priority is the safety of the patient and the dental team. There is no point in having two emergencies to deal with instead of one. Treatment should be stopped at the first sign of difficulty. This may be the patient reporting something—they often have very good insight into seizure progression. It is important to note, however, that not all patients report a prodromal stage. Seizures can occur dramatically and unannounced.

Patients should be allowed to seizure freely with the removal of any objects from the area which may hurt them. The airway should be maintained if it is safe to do so and oxygen may be administered. The dental team should not put itself in danger by trying to take out anything in the patient’s mouth etc. Intervention should be limited to airway maintenance.

A useful adjunct to treatment is oxygen therapy and this can be safely given via a face mask. Fitting patients use a higher amount of oxygen than those who are not fitting. Ventilation may also be compromised by the fit activity. This will lead to hypoxia, which may precipatate further fitting.

Recovery phase

Recovery can vary widely. Some patients will recover very quickly and show little lasting consequences. More commonly, the patient will be slow to recover and be very tired for some time afterwards. Treatment will not be completed that day and discussion of future plans should be postponed. It is vital that the patient feels secure, protected, and not embarrassed in the dental setting, so they must be dealt with very sympathetically throughout. Reassurance in the immediate post-seizure phase is very helpful.


Follow-up care will depend on the history and severity of the seizure but, if in any doubt, medical help should be sought. It is particularly important that medical help is sought if the fit is unusual for the patient in severity, duration, or provoking factor. Any patient who fits and has no previous history must be sent for urgent investigation.

Delayed treatment

If fitting is very prolonged (longer than five minutes) or recurring seizures occur, this is classed as status epilepticus and the patient requires immediate emergency hospital admission. Cerebral damage can occur if this is delayed. The patient will be given anti-seizure medication in the accident and emergency department.

Stroke (cerebrovascular accident)

The brain needs around 20% of the total blood volume at any time. If this blood flow is interrupted for even a short time, then neurone death and brain ischaemia are a risk. There are two principle types of stroke:

  • Ischaemic strokes occur as a result of blood vessel occlusion

  • Haemorrhagic strokes occur as a result of blood vessel rupture.


  • Can be difficult to diagnosis

  • Signs and symptoms can be subtle

  • Confusion

  • Muscle weakness

  • Inability to speak

  • Loss of consciousness.

Immediate management

  • Stop treatment

  • Establish level of consciousness

  • Maintain airway if necessary

  • High-flow oxygen via face mask

  • Arrange immediate transfer to hospital

  • Reassure patient

  • Monitor patient.


  • Faint

  • Other CNS emergencies.

Risk factors

  • Elderly

  • More common in men than women

  • Hypertension

  • Smoking

  • Obesity

  • Ischaemic heart disease (e.g. angina)

  • Previous stroke.

Diagnosis in the dental surgery

This can be a very difficult diagnosis to make. The symptoms can range from apparent mild confusion, through loss of speech, to a full stroke causing immediate collapse and possibly cardiac arrest.

Dentists are not expected to know the details of stroke diagnosis other than to have a low threshold of suspicion and seek help quickly. No sign or symptom should be ignored and clinicians should have a particularly low threshold of suspicion in the high-risk groups. Strokes occur most commonly in the elderly, with men at greater risk than women.

The difficulty in diagnosis due to the wide variation in clinical effects can present a problem for the dental team. A false positive diagnosis, where management is initiated for a patient who has not had a stroke is better than a false negative where a patient who has suffered a stroke receives no treatment.

Stroke has the basic risk pattern of other ischaemic disease. Although simplified, it is useful to think of those at risk of a myocardial infarction as also at risk of a stroke. This includes:

  • Smoking

  • Obesity

  • Hypertension

  • Diabetes.

A previous stroke significantly increases the patient’s risk and a careful medical history should pick this up.


Dental treatment should be stopped immediately. Patients may show immediate weakness on one side of their body, most easily seen on the face by the dental surgeon. This is not to be confused with the temporary phenomenon of facial nerve paralysis after local anaesthetic injection. Patients may not be able to communicate.

In some cases, patients may be completely unable to speak; in others, patients may be able to speak but may be unable to recall certain words. In such situations, when talking, the patient may pause and be apparently searching for words. In more extreme cases, patients may lose consciousness and the airway must be maintained as a priority. Oxygen should be given via a face mask.

Prompt transfer to hospital is the key. Mortality and morbidity can be significantly reduced with immediate assessment and care in the form of a specialist stroke team.

Patients should be reassured and their condition should be explained. They will be very apprehensive and will benefit from a well-managed approach to their care. It should be emphasized that help will be sought very promptly.

The patient should be maintained in a comfortable position. If the blood pressure is raised and the patient is conscious, they should be maintained with the head slightly above the heart. The use of sedative agents is to be discouraged.

It is also vital to have members of the team to deal with any family members who may be present. The relatives will inevitably be concerned and may wish to be with the patient. It is important that, prior to them seeing the patient, they receive an explanation of what has occurred, as well as what to expect when they see their relative.

Transient ischaemic attack

Transient ischaemic attacks (TIAs) are self-limiting, temporary events caused by non-permanent interruption to the cerebral perfusion. TIAs may be an early warning of a full stroke.

TIAs normally last for between 2 and 10 minutes. They have been described as being as short as 10 seconds or as long as 1 hour.


  • Can be difficult to diagnosis

  • Clinical signs depend on area of the brain affected

  • Transient numbness or weakness of the legs or arms

    • may be described as ‘pins and needles’

  • Transient monocular blindness

    • black or grey shadow spreading and receding over all or part of the visual field of one eye

  • Consciousness often unimpared

  • Thought processes slowed.

Immediate management

  • Stop treatment

  • Establish level of consciousness

  • Maintain airway if necessary

  • High-flow oxygen via face mask

  • Reassure patient

  • Monitor patient

  • Arrange for transfer to hospital.


Other CNS emergencies.

Risk factors

  • As for a cerebrovascular accident (CVA)

  • Patient who has regular TIAs.

Diagnosis in the dental surgery

As with a CVA, the diagnosis of a TIA can be extremely difficult. It can also be difficult to distinguish between a CVA and a TIA.

In the case of a TIA, if the patient gives a history of having such episodes, the effects that the episodes have had on the patient can give a good guide, as the symptoms in a particular patient tend to be consistent.

If any of the symptoms described above are present, then the emergency medical services should be called. In patients who have no previous history of a CVA or TIA, a first TIA may be a warning sign of a CVA, particularly if it lasts for more than an hour.


The management of the TIA is essentially the same as for a CVA. Even if the patient has a regular history of TIAs, it is wise to seek emergency medical help. If, after assessment, it is decided that hospitalization is not required, the patient should not drive home, and should be accompanied by a responsible adult.