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Archive for the ‘Neuro-imaging’ Category

Epidural Haematomas

Thursday, August 21st, 2014

This is the non-contrast CT (Figure 1) of a patient with an acute right-sided epidural haematoma . The skull vault is a tight space and the haematoma is causing significant mass effect, resulting in mid-line shift (the right cerebral hemisphere is shifted to the left as it can be seen crossing the mid-line). The epidural space is a potential space located between the inner surface of the skull and the tightly adherent periosteal dura. The middle meningeal artery, a branch from the external carotid artery, supplies the dura and runs along this space. Grooves, which are formed by this artery and its branches, can often be seen on the inner surface of the skull. Epidural haematomas are often caused by direct trauma to the skull, most often resulting in a laceration of the middle meningeal artery. Around 10% of epidural haematomas are venous, as a result of a skull fracture that crosses a dural venous sinus. Over 90% of epidural haematomas are unilateral and supra-tentorial. In most cases, the epidural haematoma is found adjacent to a skull fracture – the squamous portion of the temporal bone being the most common site. Epidural haematomas are typically biconvex or ‘lens-shaped’. This characteristic shape is because the periosteal dura is tightly adherent to the inner skull. As the epidural haematoma expands, it strips away the dura away from the inner skull, forming the characteristic lens-shape of the haematoma. Also, as the dura is tightly attached to sutures, epidural haematomas rarely cross suture lines. Most epidural haematomas are surgically evacuated.

: Figure 1

Tags:Epidural haematoma, Intracranial haemorrhage, Stroke
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Subdural Haematomas

Thursday, August 21st, 2014

Subdural haematomas are far more common than epidural haematomas and acute subdural haematomas are one of the leading causes of death and disability in patients with severe traumatic brain injury.

Subdural haematomas are due to an accumulation of blood between the dura and arachnoid. This is most often due to head injury resulting in a tear of the bridging cortical veins as they cross the subdural space to enter a dural venous sinus (usually the superior saggital sinus). Blood from the ruptured vessels could then spread quickly through the subdural space resulting in a classical crescent-shaped appearance. Subdural haematomas are usually more extensive than epidural haematomas, and easily spread along the falx, tentorium and around the anterior and middle fossa floors. In contrast to epidural haematomas, subdural haematomas may cross suture lines. Bilateral subdural haematomas may occur in 15% of cases.

Acute subdural haematoma

The non-contrast cranial CT shown here (Figure 1) is from an elderly patient with a recent fall and head injury resulting in an acute left-sided subdural haematoma . The haematoma is causing significant mass effect and the contents of the left cerebral hemisphere could be seen to be compressed resulting in a mid-line shift to the right cerebral hemisphere. An acute subdural haematoma is considered to be a neurosurgical emergency and requires urgent evacuation.

: Figure 1

Bilateral subacute subdural haematoma

This non-contrast cranial CT scan (Figure 2) is from a patient with bilateral subacute subdural haematoma. The haematoma on the right side is isodense . On the left side, however, there is a mixture of densities – the upper part being relative isodense, whilst the lower part hypodense . Such a mixed pattern is not uncommon and is usually due to recurrent haemorrhage into a pre-existing subdural haematoma, hence resulting in a mixture of densities.

: Figure 2

Chronic subdural haematoma

The series of CTs shown here are from 3 patients with chronic subdural haematomas (Figures 3-5). The subdural haematoma is unilateral in the first 2 cases and bilateral in the last case.

: Figure 3

: Figure 4

: Figure 5

Tags:Head injury, Intracranial haemorrhage, Stroke, Subdural haematoma
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Subarachnoid Haemorrhage

Thursday, August 21st, 2014

Subarachnoid haemorrhages are where there is an extravasation of blood into the space between the arachnoid and pia. Subarachnoid haemorrhages often develop as a result of rupture of a cerebral aneurysm (most often arising from the circle of Willis or the middle cerebral artery bifurcation) or consequent to severe head trauma. Patients with subarachnoid haemorrhage secondary to aneurysmal bleeding often present with sudden onset severe headache which is classically described by the patient as “the worst headache of my life“.

The series of non-contrast cranial CT scans shown here (Figures 1 to 6) are from a patient who presented with sudden onset of severe headache. Subarachnoid haemorrhage is present and blood can be seen at the basal cisterns . An urgent CT angiogram was arranged and a saccular aneurysm was noted at the left middle cerebral artery bifurcation. The Neurosurgical colleagues were then consulted urgently for neurosurgical intervention.

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It should be noted that the sensitivity of a non-contrast cranial CT scan in detecting subarachnoid haemorrhage reduces significantly with time, particularly if the subarachnoid haemorrhage is small. If subarachnoid haemorrhage is strongly suspected, the patient should undergo a lumbar puncture to delineate whether the presence of xanthrochromia is present. If present, this means that there are presence of red cells in the cerebro-spinal fluid. With time, the red cells breakdown, releasing haeme, which is subsequently degraded into the yellow-green pigment bilirubin causing the characteristic yellow colour in patients with xanthochromia. In contrast, if red blood cells enter the cerebrospinal fluid due to a “traumatic tap” (i.e. a small blood vessel was damaged during the lumbar puncture), there is inadequate time for the red cells to degrade and thus xanthochromia would not be present.

The non-contrast CT scans shown here are from 2 different patients with a right-sided subarachnoid haemorrhage (Figures 7 to 15). Blood could be seen at the sulci of the right parietal lobe in both cases and in the latter case (Figures 8 to 15), blood could also be seen at the sulci of the right temporal lobe as well as the right sylvian fissure .

: Figure 7

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: Figure 15

Tags:Cerebral aneurysm, Intracranial haemorrhage, Stroke, Subarachnoid haemorrhage, Xanthochromia
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Spontaneous Parenchymal Haemorrhage

Thursday, August 21st, 2014

There are a number of causes of spontaneous parenchymal haemorrhages. These include: hypertension, vascular malformations and aneurysms, neoplasm (primary or metastatic), cerebral amyloid angiopathy, use of antiplatelet agents or anti-coagulants, blood dyscrasias and drug abuse (e.g. amphetamine and cocaine use). Parenchymal haemorrhages could also be subdivided into deep versus lobar haemorrhages, where deep haemorrhages (basal ganglia, thalamus, brainstem) are much more often caused by hypertension.

Tags:Craniectomy, Deep haemorrhage, Head injury, Hydrocephalus, Hypertension, Intra-ventricular drain, Intracranial haemorrhage, Intraventricular extension of intracerbral haemorrhage, Lobar haemorrhage, Obstructive hydrocephalus, Skull fracture, Spontaneous parenchymal haemorrhage, Stroke
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Intra-cranial Haemorrhage due to Head Injury

Thursday, August 21st, 2014

Often, as a consequence of severe head injury, there may be haemorrhage within various intracranial compartments. In these 2 cases (Patient 1 – Figure 1, Patient 2 – Figures 2 to 11), both patients sustained a severe head injury. A combination of subdural , parenchymal and subarachnoid haemorrhage could be seen. In the second case, there is also evidence of a chronic left subdural haematoma , which may be due to prior head injury. Figure 11 is the bone window of the non-contrast CT and shows a thin vertical crack at the occiput of the skull, representing a skull fracture as a result of the head injury .