Neurosurgery

CASE 88: heaD trauma

history

A 17-year-old boy is brought to the emergency department by ambulance. He had been playing hockey and was struck on the head by a hockey ball approximately half an hour before admission. He lost consciousness briefly, but was able to walk from the scene. He is mildly confused, complaining of a severe headache, and has vomited four times.

examination

He has a pulse rate of 63/min and a blood pressure of 170/110 mmHg. During the course of the examination, he becomes drowsy and his GCS drops to 3/15. He has a ‘boggy swelling’ over the right temple. His right pupil is dilated.

INVESTIGATIONS

a Ct scan of the head is shown in Figure 88.1.

Figure 88.1 Computerized tomography scan of the head. (reproduced with kind permission from liebenberg W. a. et al. 2006. Neurosurgery Explained. vesuvius books ltd.)

Questions

•What is the diagnosis?

•What is the explanation for his vital signs?

•How should this patient be managed?

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100 Cases in Surgery

ANSWER 88

This young man has sustained an extradural bleed. A direct blow to the temporo-parietal area is the commonest cause of an extradural haematoma. The bleed is normally arterial in origin. In 85 per cent of cases there is an associated skull fracture that causes damage to the middle meningeal artery. Only 20 per cent of patients have the classic presentation of a lucid interval between the initial trauma and subsequent neurological deterioration.

The Cushing response refers to the presence of hypertension with an associated bradycardia resulting from raised intracranial pressure. The skull can be thought of as a closed box with no room for expansion; so when there is an arterial bleed, the pressure inside the ‘box’ increases rapidly. The CT scan demonstrates the hyperdense (white) appearance of an acute haematoma (arrow in Figure 88.2). The location of the haematoma is in the ‘potential’ space between the skull and dural membrane. Expansion of the blood produces the smoothmargined convex mass seen on the image compressing the brain tissue.

Figure 88.2 Computerized tomography showing an extradural haematoma (arrow). (reproduced with kind permission from liebenberg W. a. et al. 2006.

Neurosurgery Explained. vesuvius books ltd.)

The pressure created has shifted the midline and compressed the ventricular system. Further increases in pressure can only be accommodated by downward herniation of the brainstem through the foramen magnum. The resulting brainstem ischaemia is thought to lead to the Cushing response.

This situation represents a neurosurgical emergency. Without urgent decompression the patient will die. Unlike the chronic subdural, which can be treated with Burr hole drainage, the more dense acute arterial haematoma requires a craniotomy in order to evacuate it. The GCS of 3/15 would indicate that this patient is unlikely to be able to maintain his own airway and will almost certainly require intubation and ventilation prior to CT scanning.

KEY POINTS

•only 20 per cent of patients have the classical lucid interval.

•extradural haematomas are most commonly caused by damage to the middle meningeal artery.

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Neurosurgery

CASE 89: loWer baCK pain

history

A 40-year-old man presents to his general practitioner with lower back pain and pain radiating down his right leg. The pain started as he was lifting a wardrobe in the bedroom. Since then he has also noticed that his foot feels ‘strange’, and he catches it every time he walks up stairs. On direct questioning, he says he feels slightly bloated and has not passed urine since the morning. He is normally fit and healthy. He takes no regular medication. He smokes 5 cigars a day and drinks 30 units of alcohol a week. He is married and works as a structural engineer.

examination

His vital signs are normal. Abdominal examination reveals a palpable mass in the suprapubic region. Examination of the lumbar spine is normal. The power in his legs is reduced, with weakness of ankle dorsiflexion and the extensor hallucis longus. He has reduced pinprick sensation over the lateral aspect of his right foot. The sensation around his perineum is abnormal. He has an absent ankle reflex on the right. A digital rectal examination reveals reduced anal tone. His pedal pulses are palpable.

Questions

•What is the likely diagnosis?

•What are the initial stages in this man’s management?

•What investigation should be arranged?

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100 Cases in Surgery

ANSWER 89

This man has cauda equina syndrome.

The spinal cord tapers and ends at the level between the first and second lumbar vertebrae in the average adult. The most distal part of the spinal cord is called the conus medullaris, and its tapering end continues as the filum terminale. Distal to the end of the spinal cord are the nerve roots, which have the appearance of a horse’s tail, hence the Latin term ‘cauda equina’.

Cauda equina syndrome occurs when there is compression of the nerve roots at this level. There are a number of causes, including traumatic injury, spinal stenosis, spinal neoplasm, schwannomas, ependymomas, inflammatory conditions, and infection. However, as in this case, the likely cause is intervertebral disc herniation, which is the responsible for up to 15 per cent of cases. Over 90 per cent of disc herniations occur at the L4–L5 or L5–S1 levels.

The important features in this case are the presence of urogenital signs and symptoms. The palpable suprapubic mass is his bladder, as he has developed urinary retention. The abnormal sensation around his perineum, which is typically described as ‘saddle anaesthesia’, is pathognomonic. A digital rectal examination is useful in determining anal tone and is also used to determine the severity of the neurological compromise. The likely level of compression in this case is L5/S1, as suggested by weakness of ankle dorsiflexion and extensor hallucis longus. He also has reduced sensation over the lateral aspect of his foot (L5) and loss of the ankle jerk reflex (S1/S2).

It should be possible to accurately determine the level of neurological compromise by detailed neurological examination (Table 89.1). An urgent magnetic resonance imaging (MRI) scan of the lumbar spine is performed to give detailed information regarding the exact location and nature of the pathology. The patient should be referred urgently to a spinal centre once the diagnosis has been confirmed.

Table 89.1 Summary of the Clinical Findings in Lower-Limb Neurological Disease

KEY POINTS

•90 per cent of disc herniations occur at the l4–l5/l5–S1 levels.

•an urgent mri scan of the spine should be performed in any patient with back pain and urogenital signs or symptoms.

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