Head Trauma

What are the different causes of head trauma?

• Road traffic accidents
• Assault
• Home and occupational accidents
• Falls
• Bicycle or horse riding accidents

Why does head trauma cause facial palsy?

Skull fracture to the temporal bone (through which the facial nerve travels) is responsible for causing facial palsy. This is because the facial nerve travels through a small bony channel where the nerve can get crushed either by a blow to the head, or the swelling afterwards. This can result in temporary or permanent damage to one or both of the facial nerves. Because significant force is needed to fracture this particularly strong bone, other injuries are often present too — including, in some cases, injury to the neck (cervical spine), which is why other injuries are often checked for alongside any facial nerve damage.

What sort of fractures to the temporal bone cause facial palsy?

• The most common type of fracture to the temporal bone is a longitudinal fracture (a fracture that follows the long axis of the bone). A longitudinal fracture accounts for 75 per cent of all temporal bone fractures. These fractures are caused by a blow to the side of the head. The fracture tends to run along the base of the ear canal; this can result in a ruptured eardrum and bleeding from the ear can occur. Around 1 in 5 people with this type of fracture will develop facial nerve damage.
• Less common is a transverse fracture of the temporal bone (a fracture at right angles to the axis of the bone). These tend to be more serious, as the force needed to cause such damage is intense. There is a strong likelihood of ear damage as often the fracture will affect the inner ear area, resulting in hearing loss and balance problems. Facial nerve damage is much more common with this type of fracture, affecting 50-80% of cases.
• Doctors sometimes also describe these fractures based on whether or not they affect the delicate structures of the inner ear — sometimes called ‘otic capsule sparing’ (not affecting the inner ear) or ‘otic capsule disrupting’ (affecting the inner ear). If the inner ear is affected, there’s a much higher chance of facial nerve damage.

What are the symptoms?

Facial palsy after head trauma

The complicating factor in head trauma is that commonly, other life-threatening issues are occurring, and require a great deal of time and attention before the temporal bone fracture is addressed. Moreover, a good assessment of facial function requires a cooperative patient, and many patients are in a coma following head trauma, making thorough examination of nerve function impossible.

In the first stages, there may not be any obvious symptoms that the facial nerve has been damaged. This is because medical staff may be busy preserving life, or the person may be in a coma, or under anaesthetic. In these circumstances there may be no facial movements to observe, and therefore any weakness in the facial muscles or facial movements will go undetected.

Symptoms of facial nerve damage or facial paralysis are usually one-sided, but damage to both sides of the skull can occur in rare circumstances. The symptoms will be as follows:

• Difficulty or inability to blink or close the affected eye.
• Difficulty or inability to carry out a range of facial movements and/or expressions, such as smiling, whistling and frowning.
• Difficulty chewing food, or losing food from the corner of the mouth.
• Difficulty drinking, with fluids leaking from the corner of the mouth.
• Difficulty speaking, particularly with sounds that need the lips to come together, such as ‘p’ and ‘b’.
• In a small number of cases, double vision (diplopia), if a nearby nerve controlling eye movement is also affected.

See symptoms of facial palsy for more information.

How can damage to the facial nerve be diagnosed?

• It can be difficult for medical or nursing staff at first. They may be concentrating on life support or other injuries in the early hours following injury.
• Commonly, it is not the fracture to the temporal bone itself that causes damage to the facial nerve, but swelling within the tight bony canal through which the nerve runs. Since there is no room for swelling to occur, the nerve gets ‘squeezed’ within the facial canal, leading to nerve malfunction. In this situation, usually the facial muscles are working normally right after the injury, but become weak over several hours or days, as the swelling develops.
• Computerised tomography (CT scan) of the brain or magnetic resonance imaging (MRI) of the brain may identify damage to the facial nerve.
• Regular observation by medical and nursing staff will allow them to notice whether facial movement is the same on both sides.
• Regular observation will alert staff to any problems the patient may have with eye closure or blinking.

What are the treatments in the early stage following injury?

• Medication may be given to reduce the swelling.
• An operation called ‘facial nerve decompression’ may be carried out to relieve the squeezing or pressure on the nerve. However, some clinicians feel that this is an unnecessary procedure because in many cases the pressure on the nerve will recover by itself.
• The main concern in the early stages of recovery is that the eye is protected if blink and eye closure have been affected. Administration of eye drops to keep the eye lubricated is essential. Taping the eye closed at night or when sleeping will also be essential in maintaining a healthy comfortable eye and to preserve vision. See the dry eye patient guide for more information.

What are the treatment options available in the later stages following injury?

• Facial rehabilitation involves a wide range of treatment options including physiotherapy and speech and language therapy.
• Each person is individual and treatment options will vary according to your symptoms and circumstances.
• Certain surgical procedures may be available to help with eye closure and smiling.

Facial nerve injury from cuts or wounds to the face

As well as skull fractures, facial palsy can also happen if the facial nerve is directly cut or damaged by a wound to the face itself — for example, from an accident involving glass, a sharp object, or an assault. Unlike facial palsy caused by a skull fracture, this type of injury is treated with immediate surgical repair wherever possible, as this gives the best chance of recovery. One study found that repairing the nerve straightaway restored function in 97% of cases, compared with 87% when repair was delayed by up to 18 months[1].

Sources

1. Kannan RY, Hills A, Shelley MJ, et al. Immediate compared with late repair of extracranial branches of the facial nerve: a comparative study. Br J Oral Maxillofac Surg. 2020;58(2):163-169. doi:10.1016/j.bjoms.2019.11.004.