Heat stroke can lead to dysfunction of multiple organs, including the central nervous system. Image study has revealed that damages to the surviving patients with neurological impairments mainly occur in the hippocampus and cerebellum. The MR finding that suggested these structures could be one of the vulnerable structures selectively affected by heat stroke. However, it has limitations in analyzing the integrity of neural tracts on the white matter to elucidate the varying degree of clinical manifestations.
In this study, for the first time, we conducted diffusion tensor tractograhy(DTT) to elucidate combined neural tract injuries of the cerebellar peduncle (CP)s and Papez’ circuit related to cerebellar ataxia and cognitive impairment caused by heat stroke.
Case Presentation: A 27-year-old man who was in good health previously collapsed as a stupor while working in a closed construction site for 6 hours on a hot summer day (ambient temperature, 30~34 C). One hour after his arrival at the local emergency ward, he became comatose and hyper-thermic (42 C). He was diagnosed with a heat stroke. Laboratory data showed increased creatine kinase [7119 IU/L] with severe metabolic acidosis [PH 7.3; HCO-3, 17 mM/L]. On his admission, we immediately cooled his body and the body temperature was recovered normal range post-onset 6 hours. The ADC maps of 6 hour of the event showed decreased ADC on medio-posterior part of right temporal lobe, which located posterior part of hippocampus. Right superior cerebellar peduncle(CP) and pons also showed decreased ADC [Figure 1-A].
One day later, he was alert but was disoriented and presented severe ataxia and dysarthria. Two weeks later, he became oriented and responded to commands (MMSE 25), however, the symptoms of cerebellar dysfunction, such as severe dysarthria and ataxic gait were not fully relieved. Seven weeks later, he could walk independently, but showed a wide based gait pattern with left sway. He complained of memory impairment. We performed a computerized neuropsychological test [Table 1], although the patient could not perform properly the visual learning memory test due nystagmus. The patient yet showed storage and recall impairment of verbal learning memory.
Post-onset three months we performed MR with diffusion tensor imaging(DTI) to investigate the integrity of Papez circuit with probabilistic DTT and CP with fiber assignment continuous tracking(FACT) method. The T2-WI showed midly atrophic change of cerebellum (Figure 2-B).
The Papez circuit revealed that the bilateral thalamocortical tracts and right mammillothalamic tract could not be reconstructed [Figure 1-C] due to the left mammillothalamic tract injury. By contrast, the fornix and cingulum remain relatively intact. The three CPs showed injury of middle CP [Figure 1-D].
Conclusion: In the current study, using DTT we demonstrated injuries of the Papez circuit as well as CP in a patient with heat stroke. |
