physics

Subgaleal hemorrhage

Subgaleal hemorrhage is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Subgaleal hemorrhage rather than just read about it. In short: Subgaleal hemorrhage, also known as subgaleal hematoma, is bleeding in the potential space between the skull periosteum and the scalp galea aponeurosis (dense fibrous tissue surrounding the skull). Symptoms The diagnosis is generally clinical, with a fluctuant boggy mass developing over the scalp (especially over the occiput) with superficial skin bruising.

Key takeaways

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Reference excerpt

Subgaleal hemorrhage, also known as subgaleal hematoma, is bleeding in the potential space between the skull periosteum and the scalp galea aponeurosis (dense fibrous tissue surrounding the skull).

Symptoms The diagnosis is generally clinical, with a fluctuant boggy mass developing over the scalp (especially over the occiput) with superficial skin bruising. The swelling develops gradually 12–72 hours after delivery, although it may be noted immediately after delivery in severe cases. Subgaleal hematoma growth is insidious, as it spreads across the whole calvaria and may not be recognized for hours to days. If enough blood accumulates, a visible fluid wave may be seen. Patients may develop periorbital ecchymosis ("raccoon eyes"). Patients with subgaleal hematoma may present with hemorrhagic shock given the volume of blood that can be lost into the potential space between the skull periosteum and the scalp galea aponeurosis, which has been found to be as high as 20-40% of the neonatal blood volume in some studies. The swelling may obscure the fontanel and cross cranial suture lines, distinguishing it from cephalohematoma, in which the bleed is confined by its subperiosteal location. Patients with subgaleal hemorrhage may also have significant hyperbilirubinemia due to resorption of hemolyzed blood. Laboratory studies may demonstrate reduced hemoglobin and hematocrit due to blood loss into the subgaleal space, and coagulation studies may reflect an underlying coagulopathy. Mortality has been reported to occur in 12-14% of cases, generally as a consequence of massive blood loss presenting with shock, often in the setting of uncorrected coagulopathy. However, with early identification and prompt treatment, the prognosis is good, and there are usually no long-term consequences.

Causes The majority of neonatal cases (90%) result from applying a vacuum to the head at delivery (ventouse-assisted delivery). The vacuum assist ruptures the emissary veins (i.e., connections between dural sinus and scalp veins) leading to accumulation of blood under the aponeurosis of the scalp muscle and superficial to the periosteum. Additionally, subgaleal hematoma has a high frequency of occurrence of associated head trauma (40%), such as intracranial hemorrhage or skull fracture. The occurrence of these features does not correlate significantly with the severity of subgaleal hemorrhage.

Diagnosis Early recognition of this injury is crucial for survival. Infants who have experienced a difficult operative delivery or are suspected to have a SGH require ongoing monitoring including frequent vital signs (minimally every hour), and serial measurements of hematocrits and their occipital frontal circumference, which increases 1 cm with each 40 mL of blood deposited into the subgaleal space. Head imaging, using either CT or MRI, can be useful for differentiating subgaleal hemorrhage from other sources of cranial bleeding. Head ultrasound is useful for the diagnosis of SGH in the hands of an operator experienced in imaging the neonatal head and scalp, and is preferable to CT due to lack of ionizing radiation. Coagulation studies are required to detect coagulopathy that may be associated with the bleeding.

Management Management consists of vigilant observation over days to detect progression and, if required, manage complications (e.g. hemorrhagic shock, unconjugated hyperbilirubinemia and jaundice from hemolyzed red blood cells). The subgaleal space is capable of holding up to 40% of a newborn baby's blood and can therefore result in acute shock and death. Fluid bolus may be required if blood loss is significant and the patient becomes tachycardic. Transfusion and phototherapy may be necessary. Investigation for coagulopathy may be indicated.

See also Caput succedaneum Cephal Cephalohematoma Hematoma Raccoon eyes

References

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Illustrations

Worked examples

Example 1 — a first encounter with Subgaleal hemorrhage

Start with the simplest possible case. Write down what Subgaleal hemorrhage claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Subgaleal hemorrhage before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Subgaleal hemorrhage ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Subgaleal hemorrhage

In research: Subgaleal hemorrhage appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Subgaleal hemorrhage in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Subgaleal hemorrhage is common in secondary-school and first-year university syllabi. It links to neighbouring topics Birth trauma (physical), Neurological disorders, so understanding it makes those chapters shorter.
In everyday life: Look for Subgaleal hemorrhage outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Subgaleal hemorrhage in 20 minutes

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Frequently asked questions

What is Subgaleal hemorrhage in simple terms?

Subgaleal hemorrhage, also known as subgaleal hematoma, is bleeding in the potential space between the skull periosteum and the scalp galea aponeurosis (dense fibrous tissue surrounding the skull). Symptoms The diagnosis is generally clinical, with a fluctuant boggy mass developing over the scalp (…

Why does Subgaleal hemorrhage matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Subgaleal hemorrhage?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Subgaleal hemorrhage.