Ethmoid hematoma is a progressive and locally destructive disease of horses. It is indicated by a mass in the paranasal sinuses that resembles a tumor, but is not neoplastic by any means. The origins and causes of the ethmoid hematoma are generally unknown. Large hematomas usually start within the ethmoid labyrinth, and smaller ones tend to begin on the sinus floor.

The hematoma usually extends into the nasal passage. A growing hematoma causes pressure necrosis of the bone surrounding the hematoma, but only on rare occasions does it cause facial distortion. It is most commonly seen in horses older than six years. Mild, persistent, spontaneous, intermittent, and unilateral epistaxis is the most common sign clinically.

Diagnosis of the condition is best suited to endoscopy; the lesion can be seen extending into the nasal passages on endoscopic examination and can be demonstrated on radiographs. Further elucidation can be obtained with MRI or CT in cases which are more widespread or invasive.

Patients with arachnoid cysts may never show symptoms, even in some cases where the cyst is large. Therefore, while the presence of symptoms may provoke further clinical investigation, symptoms independent of further data cannot—and should not—be interpreted as evidence of a cyst's existence, size, location, or potential functional impact on the patient.

Symptoms vary by the size and location of the cyst(s), though small cysts usually have no symptoms and are discovered only incidentally. On the other hand, a number of symptoms may result from large cysts:

- Cranial deformation or macrocephaly (enlargement of the head), particularly in children

- Cysts in the suprasellar region in children have presented as bobbing and nodding of the head called bobble-head doll syndrome.

- Cysts in the left middle cranial fossa have been associated with ADHD in a study on affected children.

- Headaches. A patient experiencing a headache does not necessarily have an arachnoid cyst.

- In a 2002 study involving 78 patients with a migraine or tension-type headache, CT scans showed abnormalities in over a third of the patients, though arachnoid cysts only accounted for 2.6% of patients in this study.

- A study found 18% of patients with intracranial arachnoid cysts had non-specific headaches. The cyst was in the temporal location in 75% of these cases.

- Seizures

- Hydrocephalus (excessive accumulation of cerebrospinal fluid)

- Increased intracranial pressure

- Developmental delay

- Behavioral changes

- Nausea

- Hemiparesis (weakness or paralysis on one side of the body)

- Ataxia (lack of muscle control)

- Musical hallucination

- Pre-senile dementia, a condition often associated with Alzheimer's disease

- In elderly patients (>80 years old) symptoms were similar to chronic subdural hematoma or normal pressure hydrocephalus:

- Dementia

- Urinary incontinence

- Hemiparesis

- Headache

- Seizures

The diagnosis is generally a clinical one, 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. The hematoma spreads across the whole calvaria as its growth is insidious and may not be recognized for hours. If enough blood accumulates a visible fluid wave may be seen. Patients can develop raccoon eyes.

Patients with subgaleal hematoma may present with hemorrhagic shock. The swelling may obscure the fontanel and cross suture lines (distinguishing it from cephalohematoma). Watch for significant hyperbilirubinemia. The long-term prognosis is generally good. Laboratory studies consist of a hematocrit evaluation.

Arachnoid cysts can be found on the brain or on the spine. Intracranial arachnoid cysts usually occur adjacent to the arachnoidal cistern. Spinal arachnoid cysts may be extradural, intradural, or perineural and tend to present with signs and symptoms indicative of a radiculopathy.

Arachnoid cysts may also be classified as primary (congenital) or secondary (acquired) and have been reported in humans, cats, and dogs.

Arachnoid cysts can be relatively or present with symptoms; for this reason, diagnosis is often delayed.

Subgaleal hemorrhage or hematoma is bleeding in the potential space between the skull periosteum and the scalp galea aponeurosis.

A hematoma (US spelling) or haematoma (UK spelling) is a localized collection of blood outside the blood vessels, due to either disease or trauma including injury or surgery and may involve blood continuing to seep from broken capillaries. A hematoma is initially in liquid form spread among the tissues including in sacs between tissues where it may coagulate and solidify before blood is reabsorbed into blood vessels. An ecchymosis is a hematoma of the skin larger than 10mm.

They may occur among/within many areas such as skin and other organs, connective tissues, bone, joints and muscle.

A collection of blood (or even a hemorrhage) may be aggravated by anticoagulant medication (blood thinner). Blood seepage and collection of blood may occur if heparin is given via an intramuscular route; to avoid this, heparin must be given intravenously or subcutaneously.

It is not to be confused with hemangioma, which is an abnormal buildup/growth of blood vessels in the skin or internal organs.

Symptoms of subdural hemorrhage have a slower onset than those of epidural hemorrhages because the lower pressure veins bleed more slowly than arteries. Therefore, signs and symptoms may show up in minutes, if not immediately but can be delayed as much as 2 weeks. If the bleeds are large enough to put pressure on the brain, signs of increased ICP (intracranial pressure) or damage to part of the brain will be present.

Other signs and symptoms of subdural hematoma can include any combination of the following:

- A history of recent head injury

- Loss of consciousness or fluctuating levels of consciousness

- Irritability

- Seizures

- Pain

- Numbness

- Headache (either constant or fluctuating)

- Dizziness

- Disorientation

- Amnesia

- Weakness or lethargy

- Nausea or vomiting

- Loss of appetite

- Personality changes

- Inability to speak or slurred speech

- Ataxia, or difficulty walking

- Loss of muscle control

- Altered breathing patterns

- Hearing loss or hearing ringing (tinnitus)

- Blurred Vision

- Deviated gaze, or abnormal movement of the eyes.

Symptoms may include visible discoloring (ecchymosis), breast pain, and swelling.

The symptoms may be similar to those of fibrocystic breast changes.

Raccoon eye/eyes (also known in the United Kingdom and Ireland as panda eyes) or periorbital ecchymosis is a sign of basal skull fracture or subgaleal hematoma, a craniotomy that ruptured the meninges, or (rarely) certain cancers. Bilateral hemorrhage occurs when damage at the time of a facial fracture tears the meninges and causes the venous sinuses to bleed into the arachnoid villi and the cranial sinuses. In layman's terms, blood from skull fracture seeps into the soft tissue around the eyes. Raccoon eyes may be accompanied by Battle's sign, an ecchymosis behind the ear. These signs may be the only sign of a skull fracture, as it may not show on an X-ray. They may not appear until up 2–3 days after the injury. It is recommended that the patient not blow their nose, cough vigorously, or strain to prevent further tearing of the meninges.

Raccoon eyes may be bilateral or unilateral. If bilateral, it is highly suggestive of basilar skull fracture, with a positive predictive value of 85%. They are most often associated with fractures of the anterior cranial fossa.

Raccoon eyes may also be a sign of disseminated neuroblastoma or of amyloidosis (multiple myeloma).

Depending on cause, raccoon eyes always require urgent consultation and management, that is surgical (facial fracture or post-craniotomy) or medical (neuroblastoma or amyloidosis).

Subdural hematomas are divided into acute, subacute, and chronic, depending on the speed of their onset. Acute subdural hematomas that are due to trauma are the most lethal of all head injuries and have a high mortality rate if they are not rapidly treated with surgical decompression.

Acute bleeds often develop after high speed acceleration or deceleration injuries and are increasingly severe with larger hematomas. They are most severe if associated with cerebral contusions. Though much faster than chronic subdural bleeds, acute subdural bleeding is usually venous and therefore slower than the typically arterial bleeding of an epidural hemorrhage. Acute subdural bleeds have a high mortality rate, higher even than epidural hematomas and diffuse brain injuries, because the force (acceleration/deceleration) required to cause them causes other severe injuries as well. The mortality rate associated with acute subdural hematoma is around 60 to 80%.

Chronic subdural bleeds develop over a period of days to weeks, often after minor head trauma, though such a cause is not identifiable in 50% of patients. They may not be discovered until they present clinically months or years after a head injury. The bleeding from a chronic bleed is slow, probably from repeated minor bleeds, and usually stops by itself. Since these bleeds progress slowly, they present the chance of being stopped before they cause significant damage. Small chronic subdural hematomas, those less than a centimeter wide, have much better outcomes than acute subdural bleeds: in one study, only 22% of patients with chronic subdural bleeds had outcomes worse than "good" or "complete recovery". Chronic subdural hematomas are common in the elderly.

Fever, headache, and neurological problems, while classic, only occur in 20% of people with brain abscess.

The famous triad of fever, headache and focal neurologic findings are highly suggestive of brain abscess. These symptoms are caused by a combination of increased intracranial pressure due to a space-occupying lesion (headache, vomiting, confusion, coma), infection (fever, fatigue etc.) and focal neurologic brain tissue damage (hemiparesis, aphasia etc.).

The most frequent presenting symptoms are headache, drowsiness, confusion, seizures, hemiparesis or speech difficulties together with fever with a rapidly progressive course. Headache is characteristically worse at night and in the morning, as the intracranial pressure naturally increases when in the supine position. This elevation similarly stimulates the medullary vomiting center and area postrema, leading to morning vomiting.

Other symptoms and findings depend largely on the specific location of the abscess in the brain. An abscess in the cerebellum, for instance, may cause additional complaints as a result of brain stem compression and hydrocephalus. Neurological examination may reveal a stiff neck in occasional cases (erroneously suggesting meningitis).

A breast hematoma may appear due to direct trauma to the breast, for example from a sports injury or a road accident, for example a vehicle collision in which a seat belt injury occurs.

Hematoma can also be a consequence of breast surgery, usually due to post-operative bleeding. Bleeding may occur shortly after the intervention or a number of days later and can occur for cosmetic surgery (for example breast reduction or breast enhancement) and for non-cosmetic surgery (for example lymph node removal, lumpectomy, or mastectomy). More rarely, hematoma can result from breast biopsy.

Rarely, a breast hematoma can also occur spontaneously due to a rupture of blood vessels in the breast, especially in persons with coagulopathy or after long-term use of blood-thinning drugs such as aspirin or ibuprofen.

A rectus sheath hematoma is an accumulation of blood in the sheath of the rectus abdominis muscle. It causes abdominal pain with or without a mass.

The hematoma may be caused by either rupture of the epigastric artery or by a muscular tear. Causes of this include anticoagulation, coughing, pregnancy, abdominal surgery and trauma. With an ageing population and the widespread use of anticoagulant medications, there is evidence that this historically benign condition is becoming more common and more serious.

On abdominal examination, people may have a positive Carnett's sign.

Most hematomas resolve without treatment, but they may take several months to resolve.

Many lymphoceles are asymptomatic. Larger lymphoceles may cause symptoms related to compression of adjacent structures leading to lower abdominal pain, abdominal fullness, constipation, urinary frequency, and edema of the genitals and/or legs. Serious sequelae could develop and include infection of the lymphocele, obstruction and infection of the urinary tract, intestinal obstruction, venous thrombosis, pulmonary embolism, chylous ascites and lymphatic fistula formation.

On clinical examination the skin may be reddened and swollen and a mass felt. Ultrasonography or CT scan will help to establish a diagnosis.

Other fluid collections to be considered in the differential diagnosis are urinoma, seroma, hematoma, as well as collections of pus. Also, when lower limb edema is present, venous thrombosis needs to be considered.

A lymphocele is a collection of lymphatic fluid within the body not bordered by epithelial lining. It is usually a surgical complication seen after extensive pelvic surgery (such as cancer surgery) and is most commonly found in the retroperitoneal space. Spontaneous development is rare.

Some hematomas are visible under the surface of the skin (commonly called bruises) or possibly felt as masses/lumps. Lumps may be caused by the limitation of the blood to a sac, subcutaneous or intramuscular tissue space isolated by fascial planes. This is a key anatomical feature that helps prevent injuries from causing massive blood loss. In most cases the hematoma such as a sac of blood eventually dissolves; however, in some cases they may continue to grow such as due to blood seepage or show no change. If the sac of blood does not disappear, then it may need to be surgically cleaned out/repaired.

The slow process of reabsorption of hematomas can allow the broken down blood cells and hemoglobin pigment to move in the connective tissue. For example, a patient who injures the base of his thumb might cause a hematoma, which will slowly move all through the finger within a week. Gravity is the main determinant of this process.

Hematomas on articulations can reduce mobility of a member and present roughly the same symptoms as a fracture.

In most cases, movement and exercise of the affected muscle is the best way to introduce the collection back into the blood stream.

A mis-diagnosis of a hematoma in the vertebra can sometimes occur; this is correctly called a hemangioma (buildup of cells) or a benign tumor.

The primary symptom, hemorrhage, presents differently depending on the degree of injury, with the symptoms of major hemorrhage, shock, abdominal pain, and distention being clinically obvious. Minor hemorrhage often presents as upper left quadrant pain. Patients with unexplained left upper quadrant pain, particularly if there is evidence of hypovolemia or shock, are generally inquired regarding any recent trauma.

CSF rhinorrhoea refers to the drainage of cerebrospinal fluid through the nose. Measures of CSF components such as glucose have been used in the past, but are neither sensitive nor specific; beta-2 transferrin, however, has been shown to have a high positive predictive value. It has also been noted to be characterized by unilateral discharge.

It is a sign of basal skull fracture. Management includes watchful waiting - leaks often stop spontaneously; if this does not occur then neurosurgical closure is necessary to prevent the spread of infection to the meninges.

Other signs of basal skull fracture includes CSF otorrhoea (drainage of CSF through the ear). It can have devastating complications in some patients, as the communication between the nasal cavity and the cerebrospinal fluid and CNS can result in bacterial infections of the CNS that can have catastrophic effects on the patient.

CSF rhinorrhoea can also be a symptom of a pituitary adenoma.

Spontaneous CSF rhinorrhea. The most common congenital or acquired defect in the skull base bones (anterior cranial fossa) at the spontaneous nasal liquorrhea localized in following formation:

- sphenoid sinus (43%)

- ethmoid bone (29%)

- cribriform plate (29%)

The symptoms of a perianal hematoma can present over a short period of time. Pain, varying from mild to severe, will occur as the skin surrounding the rupture expands due to pressure. This pain will usually last even after the blood has clotted, and may continue for two to four days.

Subdural hematoma occurs when there is tearing of the bridging vein between the cerebral cortex and a draining venous sinus. At times they may be caused by arterial lacerations on the brain surface. Acute subdural hematomas are usually associated with cerebral cortex injury as well and hence the prognosis is not as good as extra dural hematomas. Clinical features depend on the site of injury and severity of injury. Patients may have a history of loss of consciousness but they recover and do not relapse. Clinical onset occurs over hours. A crescent shaped hemorrhage compressing the brain that does cross suture lines will be noted on CT of the head. Craniotomy and surgical evacuation is required if there is significant pressure effect on the brain.Complications include focal neurologic deficits depending on the site of hematoma and brain injury, increased intra cranial pressure leading to herniation of brain and ischemia due to reduced blood supply and seizures.

Potential complications of a nasal septal abscess include cavernous sinus thrombophlebitis, septal perforation, or saddle deformity due to cartilage necrosis.

The primary concern in any splenic trauma is internal hemorrhage, though the exact amount of hemorrhage may be small or large, depending on the nature and degree of injury. Small or minor injuries often heal spontaneously, especially in children. Larger injuries hemorrhage extensively, often causing hemorrhagic shock. A splenic hematoma sometimes ruptures, usually in the first few days, although rupture can occur from hours to even months after injury.

Epidural hematoma (EDH) is a rapidly accumulating hematoma between the dura mater and the cranium. These patients have a history of head trauma with loss of consciousness, then a lucid period, followed by loss of consciousness. Clinical onset occurs over minutes to hours. Many of these injuries are associated with lacerations of the middle meningeal artery. A "lenticular", or convex, lens-shaped extracerebral hemorrhage that does not cross suture lines will likely be visible on a CT scan of the head. Although death is a potential complication, the prognosis is good when this injury is recognized and treated.

Nasal septal hematoma is a condition affecting the nasal septum. It can be associated with trauma.

Because the septal cartilage has no blood supply of its own and receives all of its nutrients and oxygen from the perichondrium, an untreated septal hematoma may lead to destruction of the septum. Immediate drainage is necessary. Failure to recognise septal hematomas, or treat in a timely fashion, can cause a saddle nose deformity.