Post-Traumatic Subdural Hygroma : A One Year Follow up Case Report and Literature Review

Post-traumatic subdural hygroma it is an intracranial lesion, commonly misdiagnosed due to its unclear symptomatology and slow progression. Defined as the presence of cerebral spinal fluid in between the arachnoid and the duramater layers; causing a variety of symptomatology that usually depend on the amount of fluid within this space (subdural). Post traumatic subdural hygroma it’s observed in 5-20% of all blunt head injuries, although its diagnosis it’s usually rare among emergency departments. Prognosis is usually good due to the absence of severe complications and its spontaneous resolution in mostly of the cases. We present a 26-year-old male patient, with history of high impact blunt trauma, presenting ocular refractive changes and headache. After CT scan evaluation and BOLD-MRI confirmation, a bilateral fronto-parietal subdural hygroma was confirmed.

TBI is often seen in younger males that were involved in car or motorcycle accidents as well as in high impact sports lesions (Ansari-Moghaddam et al., 2013;Monsef Kasmaei et al., 2015;Ling, Hardy, & Zetterberg, 2015).This type of trauma is one of the leading causes of disability and death among patients under 25 years, especially in developing countries (Ansari-Moghaddam et al., 2013;Monsef Kasmaei et al., 2015;Carney et al., 2012).
Although CT scan or Brain MRI is often used to detect brain injury, not every lesion has detectable radiological signs, making diagnosis difficult in some scenarios (Belanger et al., 2007).
Diagnosis of PTSH its radiological; a positive CT or MRI sign accompanied by relevant clinical presentation are needed before ensuring an accurate diagnosis, nevertheless, just 13% of patients with mild traumatic brain injury who underwent CT scan imaging exhibit radiological signs of post-traumatic subdural hygroma (Todorow & Happe, 1981).

Case Report
A 26 years old male, with 15 days' history of high impact head trauma, was seen in a tertiary clinical center in Quito, Ecuador after presenting acute intense headache and blurry vision.His relatives inform that approximately 15 days ago he fell from his bicycle while using a "fullface" helmet that could not prevent him to having one generalized tonic-clonic seizure lasting at least 1 minute, accompanied with transitory altered state of consciousness, condition that not received any medical attention.
At arrival his vital signs were normal, AT 120/70mmHg, HR: 90', RR: 20' SO2: 98% and Glasgow Coma Scale 15/15.He arrived conscious, oriented in time, place, his pupils are isochoric with normal-reactivity to light and accommodation, no signs of focal lesion or any cranial nerve affection.His only complain it´s a severe holocranial headache that is exacerbated by coughing, sneezing and Valsalva maneuvers.Additionally, a very intense discomfort was reported with minimal head movements, especially when the patient lies in prone position affecting visual acuity temporally.
The patien was sent to another hospital to obtain a normal no contrasted CT scan.When results arrived, a bilateral fronto-parietal hypodense accumulation, suggestive of some sort of subdural effusion was observed.There is no sign of intraparenchymal lesion or deviation of the medial line (Figure 1) and symptomatology did not correlated with more severe subdural hematomas.After two weeks, the patient reported significant improvement, although mild visual disturbances and some unspecific discomfort associated with head movements were still present.
One year after the accident, during the follow up appointment, a total recovery was confirmed with the patient.
No neurological signs or symptomatology was found.
As part of a medical investigation, a Magnetic Resonance Image (MRI) and functional BOLD MRI (Blood oxygen level Dependent MRI) were performed in order to confirm the absence of any subdural effusion (Figure 2).
Figure 2. MRI after one-year trauma, where the presence of radiological signs consistent with fibrosis are evident, it differentiates form chronic subdural hematoma which is hypodense The anatomical MRI showed the presence of mild subdural fibrosis, at the bilateral fronto-parietal level.On the other hand, the functional BOLD MRI showed an image compatible with neovascularization in the same areas where the subdural effusion was seen, suggesting the diagnosis of post-traumatic subdural hygroma from an inflammatory etiology (Figure 3).

Discussion
A subdural hygroma (SH) is defined as acute or chronic Cerebrospinal fluid accumulation in the subdural space, which is actually a virtual space between the arachnoid and subdural membranes (Zanini et al., 2008).
This condition represents up to 12% of all intracranial posttraumatic masses (Herold et al., 2004;Lee et al., 1996) and up to 20% of all the blunt closed head injuries (Lee, Bae, Bae, et al., 2000;Lee, 2004).It is relatively more common in patients between 10-50 years of age as a late complication of head trauma and since mostly of them are silent and resolved spontaneously, an important number might not be diagnosed (French et al., 1978;Lee, 1998;Rambarki & Rajesh, 2014).
As stated before, some studies show that normal CT scans can not always detect this type of lesion, however, when detected, the most common presentation is a bilateral subdural effusion.This effusion is located mainly within the frontoparietal lobules representing more than 77% of the cases, followed by the posterior fossa with 2.5% and very rarely within the medullar subdural space (Lee, Bae, Yoon, et al., 2000;Kabir, Jennings, & Makris, 2004;Traumatic Epidural Haematoma of the Posterior Fossa in Childhood: 16 New Cases and a Review of the Literature.-PubMed-NCBI,n. d.).
Regardless the location, subdural effusions are the result of traumatic (mechanic) and non-traumatic forces, being the first one the main etiological cause (Zanini et al., 2008).Some of the most common post traumatic reasons are those presented in patients who have undergone craniotomies, surgical resection of aneurysms, drainage of hematomas or removal of intracranial tumors (Alotaibi et al., 2014;Park et al., 2015;Van Den Berg et al., 2002).Obstetric trauma is another common cause of SH among infants, followed by head trauma, specially the shaken baby syndrome (Ebner et al., 2015;Wittschieber et al., 2015;Nixon & Soares, 2016).
Although etiology it's well known, pathogenesis of this condition is not well understood.Some theories have gained more support and include: The formation of a one-way valve allowing the passage of CSF into the subdural space, caused by a traumatic tear of the arachnoidal mater or due to the rupture of an existing arachnoids cyst (Kusuno et al., 1984;Rajesh, Bramhaprasad, & Purohit, 2012;Pillai et al., 2009).An underlying parenchymal or vascular disorder that causes a passive effusion into the subdural space (Stone et al., 1981;Maddalozzo et al., 1999;Wittschieber et al., 2015) and new formation of subdural vascularized neomembranes accompanied by increased permeability of CSF in the arachnoids membrane, which might be linked with the meningeal barrier permeability or by increasing the transmembrane pressure gradient (Thompson, Lee, & MacIntosh, 2015;Bora et al., 2015;Strahle et al., 2015).
On the other hand, the most common non-traumatic subdural hygroma in the elderly group is largely due to brain atrophy (Tanaka & Ohno, 2013).And many times triggered as a result of uncontrolled administration of hypertonic agents, hypernatremia, marked dehydration, long-term coughing or sneezing, recurrent or Valsalva maneuvers (Dierckx et al., 1988).
Subdural hygroma have been also related to infectious disease such as tuberculosis and some rare chromosomal syndromes such as Menkes disease, which is a rare disorder X-linked, characterized by alteration of copper metabolism (Jain et al., 2014;Cho et al., 2005;Fisher & Hiller 1994).
In order of frequency, the most common symptoms are: slight changes in the state of consciousness, holocranean headache which is exacerbated by movement, coughing, nausea, vomiting, they can also occur vision disorders such as diplopia or slowing of accommodation; and rarely, coma and death (Alotaibi et al., 2014;Thompson, Lee, & MacIntosh, 2015;Park et al., 2015).
Cisternography, angiography and surgical drainage were used as a diagnostic test, but currently the CT and MRI are the main diagnostic methods, the use of contrast is not recommended because there is no significant evidence of its diagnostic utility (Wittschieber et al., 2015;Duhem et al., 2006;Lee & Newberg, 2005;Nixon & Soares, 2016).
When looking to diagnose hygromas, CT scan is very useful, although some intracranial injuries should be taken into account before ruling in hygromas (Alotaibi et al., 2014).The most common differential diagnosis is made with acute subdural isodense hematomas (Huh et al., 2006;Tanaka & Ohno, 2013).To the unexperienced eye, hematomas and hygromas might look alike, being the Housefields units ranging from +10 and +16, an important tool to diagnose PRSH in the presence of cerebral effusions (Mori & Maeda, 2000).
After diagnosis, conservative treatment is the the primary election and its usually aimed at reduce symptomatology (Kumar et al., 2010).In large hygromas, when mass effect and compression is diagnosed, surgery will provide relieve (Thompson, Lee, & MacIntosh, 2015;Park et al., 2015).

Conclusions
Subdural hygromas are a relatively common but under diagnosed intracranial lesion.Etiology is not totally understood, being head trauma the most important factor related with its origin, many times its diagnosis is confused with subdural isodense hematomas.
Most cases are not detected due to poor and unspecific symptomatology; thus a suspicious eye is needed when obtaining a suspicious CT scan with unspecific symptomatology.Although most patients will present headache and diverse symptomatology, conservative treatment works well in the majority of cases.
Following up a case like this opens the possibility to understand the behavior of this pathology.On the other hand, this is the first time that a BOLD MRI was used to confirm the presence of subdural vascular activity related with previous effusion.
We recommend that all the patients with history of head trauma and unclear clinical presentation should be seen by a neurologist and a neurosurgeon to conform diagnosis and to decide the appropriate treatment.

Figure 1 .
Figure 1.CT scan performed 30 days after injury, where the presence of hypodense accumulation is evident in the subdural space, bilateral fronto-parietal level

Figure 3 .
Figure 3. BOLD MRI imaging showing hyperintensity activity within the subdural space