【Knowledge consolidation】The difference between cerebral atrophy and subdural effusion

【Brain atrophy】

Etiology: Cerebral atrophy is a decrease in the volume and number of brain tissue cells caused by various factors, secondary enlargement of the ventricles and subarachnoid space, which can occur in white matter and gray matter
, respectively or simultaneously.

The main causes are trauma, infection, drug-related, senile and other diseases
.

According to its degree and scope, it can be divided into two categories
: localized brain atrophy and diffuse brain atrophy.

Clinical: Some patients can have memory decline in the early stage, followed by disorientation, poor speech, and finally dementia

CT and MRI findings:

(1) Diffuse brain atrophy:

(1) Cerebral cortical cerebral atrophy is mainly widening (enlargement) of the sulci and cistern, and ventricular enlargement is mild or normal;

(2) White matter type brain atrophy is mainly ventricular enlargement, and the vulcibral cistern widening is mild or normal;

(3) Mixed diffuse brain atrophy, gray matter and white matter are affected, showing that the sulci, cistern and ventricles are enlarged
.

(2) Localized brain atrophy: widening
of localized sulci and cistern.

Ventricular enlargement produces a negative mass effect; Its range can be limited to a few gyrus, or it can be a lobe or one hemisphere, with unilateral ventricular enlargement and midline structures displaced
to the atrophic side of the brain.

To determine whether there is brain atrophy, visual methods are generally used in clinical work, namely:

(1) The size of the sulci, cistern and ventricle was compared with that of normal peers, and if there was significant widening, it was brain atrophy;
(2) The width of the sulci >5mm can indicate cerebral atrophy;

(3) The lateral ventricle frontal angle, occipital angle and temporal angle become round and blunt, which indicates the corresponding brain lobe atrophy, but attention should be paid to the possibility of
physiological variation.

Differentiate: ventricular enlargement due to diffuse cerebral atrophy should be differentiated from
hydrocephalus.

But simple brain atrophy:

(1) There is no abnormal low-density area in the brain parenchyma, and hydrocephalus can appear in the low-density area of interstitial edema around the ventricles;

(2) The morphology of the ventricle does not change significantly when the brain is atrophied, and when the coronary position is reconstructed, the angle between the top of the left and right ventricles becomes larger (>140°), the ventricles expand to all sides during hydrocephalus, the frontal angle of the left and right ventricles is spherical, and the angle of the top of the lateral ventricles shrinks (<120°);

(3) The third ventricle is enlarged, and hydrocephalus is more obvious than cerebral atrophy, which can be spherical;

(4) When the brain atrophies, the sulci and cistern widen, while when hydrocephalus, the sulci becomes shallow or disappears, and the cistern is not wide
.

【Subdural effusion】

Age: More common in the elderly and infants
.

Etiology: more common after trauma, can also occur after V-P surgery, after craniotomy, and after
meningitis.
Also known as subdural effusion
.

Trauma causes arachnoid tears, forming a living flap that prevents cerebrospinal fluid from flowing back into the subdural space, or after fluid enters the subdural space, the arachnoid rupture is blocked by blood clots or edema
.

The fluid in the water tumor is watery, pale yellow or reddish, and the protein content is higher
than that of cerebrospinal fluid.
Subdural hydroma is acute and chronic
.

Acute is rare and forms within hours, while chronic is wrapped
in a membrane.

CT findings: mostly occur on one or both frontal temporal bone plates
.
50% are in the double frontal area, and the anterior part of the long deep longitudinal fissure is M-shaped, showing a crescent-shaped low-density area below the inner plate, which is similar to the density of cerebrospinal fluid, with no or only slight mass performance
.
There is no cerebral edema
around.

MRI findings: on T1-weighted and T2-weighted images, subdural hydroma signaling is similar to cerebrospinal fluid, and some cases can appear as hyperintense on T1-weighted images, which may be related to the protein content in the hydroma

Clinical: can be divided into acute and chronic
.
Presents with cranial hypertension and mass.

Acute drillable drainage, chronic drill drainage or craniotomy flap plasty capsulectomy
.
A few absorb on their own
.

Senile brain atrophy is generally manifested by bilateral gyrus widening, deepening of the sulci, atrophy of the brain parenchyma, and often enlargement
of the ventricular system.

The subdural effusion is caused by trauma, unilateral is easy to identify, bilateral common frontotemporoparietal area banded low-density zone (CT), due to the mass effect, sulci, gyrus become shallow, ventricles shrink.

For patients with cerebral atrophy, the sulci and gyrus at the effusion are also shallower
than other parts.

In addition, subdural effusion often has a history of trauma, which may be accompanied by intellectual and behavioral disorders, and symptoms of cerebral compression
.

If the symptoms are not obvious, subdural effusion is generally treated conservatively, because the elderly have a large intracranial compensation space, for a large amount of effusion (>100ml, or thickness > 1.
5cm), resulting in obvious cerebral compression symptoms, surgery, generally drilling and drainage can be, but pay attention to the drainage should not be too fast, do not need dehydration diuretic drugs, pay attention to rehydration, the head position can be slightly lower, conducive to drainage
.
It can also be supplemented with hyperbaric oxygen therapy to facilitate recovery
.
It is also important to note that subdural effusions can gradually transform into chronic subdural hematomas, so CT
should be reviewed regularly in conservative patients.

In clinical practice, subdural effusion after trauma greater than 50 years of age is common, often bilateral.

In diagnosis, first look at whether there is increased intracranial pressure, and when it is not easy to identify, mannitol experimental diagnosis
should be used.
The effusion is mostly in the frontal lobe, to see if the ventricular frontal angle is compressed
.

In terms of treatment, a small amount of effusion does not need to be treated, and the large amount can dynamically observe the symptoms and CT, and when it progressively worsens, it can be drilled and drained, otherwise it is treated
conservatively.