Compensatory Neural Tract from Contralesional Fornical Body to Ipsilesional Medial Temporal Lobe in a Patient with Mild Traumatic Brain Injury: A Case Report

Role of Diffusion Tensor Imaging in the Diagnosis of Traumatic Axonal Injury in Individual Patients with a Concussion or Mild Traumatic Brain Injury: A Mini-Review

Present review paper aims to understand role of diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) in diagnosis of traumatic axonal injury (TAI), induced by head trauma, in individual patients with a concussion or mild traumatic brain injury (mTBI). Precise information on presence and severity of TAI in brain is necessary for determining appropriate therapeutic strategies. Several hundred DTI-based studies have reported TAI in concussion or mTBI. Majority of these DTI-based studies have been performed in a group of patients, whereas case studies that have reported TAI in individual patients with a concussion or mTBI are fewer. Summary of these DTI-based studies for individual patients is as follows: DTI can be used as a non-invasive tool for determining presence and severity of TAI in individual patients with concussion or mTBI. However, for diagnosis of TAI in an individual patient, several conditions are required to be met: no past history of head trauma, presence of possible conditions for TAI occurrence during head trauma, development of new clinical features after head trauma, and DTI observed abnormality of a neural structure that coincides with a newly developed clinical feature. However, further studies for a more precise diagnosis of TAI in individual patients should be encouraged.

Relation Between Memory Impairment and the Fornix Injury in Patients With Mild Traumatic Brain Injury: A Diffusion Tensor Tractography Study

OBJECTIVE

We investigated the relation between memory impairment and the fornix injury in patients with mild traumatic brain injury, using diffusion tensor tractography.

DESIGN

Eighty-six chronic patients with mild traumatic brain injury and 50 normal control subjects were recruited. Fractional anisotropy and fiber volume were measured for each reconstructed fornix. The patients were classified according to the following three types: type A (47 patients), intact integrity of both fornical crura; type B (27 patients), showed a discontinuation in either fornical crus; and type C (12 patients), discontinuations in both fornical crura. The Memory Assessment Scale was used for evaluation of memory function.

RESULTS

Fractional anisotropy and fiber volume showed weak positive correlations with global memory of Memory Assessment Scale, respectively (r = 0.303, P = 0.006; r = 0.271, P = 0.014). Significant difference in the global memory of Memory Assessment Scale was observed between type A and B and between type A and C without difference between type B and C (P < 0.05).

CONCLUSION

It seems that the diffusion tensor tractography parameters of the fornix and the integrity of fornical crus can be used as a biomarker for axonal injury of the fornix in patients with mild traumatic brain injury.

Delayed degeneration of the left fornical crus with verbal memory impairment in a patient with mild traumatic brain injury: A case report

RATIONALE

We report on a patient who showed delayed degeneration of the left fornical crus with verbal memory impairment following mild traumatic brain injury (TBI), which was demonstrated by diffusion tensor tractography (DTT). PATIENT CONCERNS:: fter flexion and hyperextension of her head to the opposite side, the patient experienced a dazed feeling for a while at the time of head trauma. The patient's Glasgow Coma Scale score was 15, and mini-mental state examination score was 30.

DIAGNOSES

A 50-year-old right-handed female with 12 years of education suffered from head trauma resulting from a car accident.

INTERVENTIONS

A The patient showed normal memory function at one year after onset: the Memory Assessment Scale (global memory: 124 (95 percentile (%ile)), verbal memory: 111 (77%ile), and visual memory: 132 (98%ile) (A percentile is a measure used in statistics indicating the value below which a given percentage of observations in a group of observations fall). However, the patient began to experience decline of memory function such as forgetfulness at approximately 1.5 years after onset. On the 2-year evaluation, she showed decrement of memory function (global memory: 108 (70%ile), verbal memory: 86 (18%ile), and visual memory: 129 (97%ile).

OUTCOMES

On 1-year DTT, the integrity of the fornix was well preserved between the fornical column and fornical crus. However, on 2-year DTT, a discontinuation was observed in the left fornical crus.

LESSONS

Delayed degeneration of the left fornical crus was demonstrated in a patient who showed delayed onset of verbal memory impairment following mild TBI.

Diffusion tensor tractography studies on mechanisms of recovery of injured fornix

The fornix, which connects the medial temporal lobe and the medial diencephalon, is involved in episodic memory as an important part of the Papez circuit. The mechanisms of recovery of an injured fornix revealed by diffusion tensor tractography in the five studies are summarized as follows: 1) recovery through the nerve tract from an injured fornical crus to the medial temporal lobe via the normal pathway of the fornical crus; 2) recovery through the nerve tract originating from an ipsi-lesional fornical body connected to the ipsi-lesional medial temporal lobe via the splenium of the corpus callosum; 3) recovery through the nerve tract from the ipsi-lesional fornical body extending to the contra-lesional medial temporal lobe via the splenium of the corpus callosum; 4) recovery through the nerve tract originating from the ipsi-lesional fornical column connected to the ipsi-lesional medial temporal lobe; and 5) recovery through the nerve tract originating from the contra-lesional fornical column connected to the ipsi-lesional medial temporal lobe via the contra-lesional medial temporal lobe and the splenium of the corpus callosum. These diffusion tensor tractography studies on mechanisms of recovery of injured fornical crus appeared to provide useful information for clinicians caring for patients with brain injury, however, studies on this topic are still in the beginning stages.

Traumatic axonal injury despite clinical phenotype of mild traumatic brain injury: a case report

OBJECTIVES

We report on a patient who suffered traumatic axonal injury (TAI) of various neural tracts despite airbag deployment following mild traumatic brain injury (TBI), which was demonstrated by diffusion tensor tractography (DTT).

CASE DESCRIPTION

A 58-year-old female patient suffered from head trauma resulting from an in-car traffic accident. At the time of head trauma, her head and face hit the deployed airbag after flexion-hyperextension-rotation injury. The patient's Glasgow Coma Scale score was 15. Since the day of head trauma, she began to feel headache and upper back pain at the mid-thoracic area. At 7 days after onset, she began to feel pain on the left hand, which spread to the right hand and leg: throbbing and cold pain without allodynia or hyperalgesia (visual analogue scale score: 5). She also felt mild weakness of all four extremities and mild memory impairment. On 4-week DTT, the corticospinal tract showed partial tearing at the subcortical white matter level in both hemispheres . The right fornical crus and right anterior cingulum were discontinued, and narrowing and partial tearing were observed in both spinothalamic tracts.

CONCLUSIONS

TAI of four kinds of neural tracts was demonstrated in a patient with mild TBI despite airbag deployment, using DTT.

Abundant unusual neural branches from the fornix in patients with mild traumatic brain injury: A diffusion tensor tractography study

OBJECTIVES

Since the introduction of diffusion tensor tractography (DTT), several studies have been reported on the mechanisms for the recovery of an injured fornix in patients with traumatic brain injury (TBI). We report on patients who showed abundant unusual neural branches from the fornix following mild TBI using DTT.

METHODS

Five patients with mild TBI who complained of memory impairment and showed preserved integrity of the fornix with abundant unusual neural branches on DTT, and eight normal subjects were recruited. DTT parameters (fractional anisotropy [FA] and fibre number) of the fornix were measured.

RESULTS

All five patients showed memory impairment on only one subscale of the Memory Assessment Scale (MAS), although the global MAS was within the normal range. The FN of the fornix was increased by more than two standard deviations in all five patients compared with that of normal subjects, while the FA value was within two standard deviations of that of normal subjects. On the DTT for the fornix of the patients, three types of unusual neural tracts from the fornix not observed in normal subjects were observed in patients.

CONCLUSION

The abundant unusual neural branches from the fornix might be a recovery phenomenon of a mildly injured fornix, although the integrity of the fornix was preserved in these patients.

Understanding the Mechanisms of Recovery and/or Compensation following Injury

Injury due to stroke and traumatic brain injury result in significant long-term effects upon behavioral functioning. One central question to rehabilitation research is whether the nature of behavioral improvement observed is due to recovery or the development of compensatory mechanisms. The nature of functional improvement can be viewed from the perspective of behavioral changes or changes in neuroanatomical plasticity that follows. Research suggests that these changes correspond to each other in a bidirectional manner. Mechanisms surrounding phenomena like neural plasticity may offer an opportunity to explain how variables such as experience can impact improvement and influence the definition of recovery. What is more, the intensity of the rehabilitative experiences may influence the ability to recover function and support functional improvement of behavior. All of this impacts how researchers, clinicians, and medical professionals utilize rehabilitation.