**5. Autoimmune encephalitis**

This category consists of heterogeneous conditions; all share the feature of autoimmunity against different components of the CNS. The antibodies may target against intraneural or cell surface molecules (synaptic receptors, ion channels, other molecules). They may be accompanied by an underlying neoplasm. Experts recommend to have this diagnosis in mind whenever facing a subacute encephalopathy with focal neurologic findings (clinically or in imaging) [50]. Dysphagia is reported in various subtypes of the disease.

Anti IgLON5 disease is a relatively novel entity characterized by sleep-related diseases like REM or non-REM parasomnias, obstructive sleep apnea, and stridor. This disease may present similar to neurodegenerative diseases. It is progressive and could be fatal (e.g. due to central hypoventilation). By early diagnosis and treatment, there is hope in halting the disease's progression to respiratory arrest. Bulbar symptoms are quite prevalent. Dysphagia is the most common bulbar symptom in this population. Other manifestations include gait instability, dysautonomia, movement disorders, supranuclear gaze palsy, and cognitive impairment [51, 52].

In a case series of 20 patients with DPPX potassium channel antibody, 15 had brainstem involvement of whom six patients experienced dysphagia along with other symptoms. DPPX potassium channel antibody is "immunoglobulin G (IgG) targeting dipeptidyl-peptidase-like protein-6 (DPPX), a regulatory subunit of neuronal Kv4.2 potassium channels" [53].

Castle et al. reported a 39-year-old patient who presented with subacute progressive behavioral changes, dysphagia, and ataxia. Anti-Ma2 was detected and cancer work-up revealed metastatic testicular cancer. Anti-Ma2 encephalitis involves the brainstem commonly. Dysphagia is present in 20% of these cases [54].

A 14-year-old boy has been reported who had dysphagia, unilateral weakness, and aggressiveness as presenting symptoms of autoimmune encephalitis caused by Hashimoto disease. The point is that the patient had no previous clinical clue of thyroiditis. Hashimoto encephalitis could manifest with a variety of clinical scenarios so it should be in mind whenever facing an autoimmune pathology of the CNS [55].

#### *Dysphagia in Neuroinflammatory Diseases of the Central Nervous System DOI: http://dx.doi.org/10.5772/intechopen.101794*

Anti-Neuronal Nuclear Autoantibody Type 2 (ANNA-2) or "anti-Ri" is an uncommon antibody detected among cases of paraneoplastic encephalitis. It could be associated with several underlying cancers. Pittock et al. detected this marker in 34 patients in 75,000 patients with suspected paraneoplastic neurologic symptoms. Brainstem symptoms including dysphagia were prevalent among these cases. Involvement of other parts of the nervous system (cortex, basal ganglia, cerebellum, spinal cord, cranial nerves, peripheral nerves, or neuromuscular junction) was also seen [56].

Autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy is a recently introduced disease. The inflammation in this disease involves meninges in addition to other parts of the CNS. It could cause headache, visual disturbance, fever, psychosis, myelitis, ataxia, abnormal movements, or autonomic dysfunction. The MRI would show linear enhancement oriented radially to the ventricles in the brain. A reported case by Li et al. highlights the possibility of dysphagia being a part of the initial presentation [57].

Dysphagia, albeit not common, could also be seen in those with IgG autoantibody targeted against neuronal cytosolic protein, neurochondrin. These cases mostly present with cerebellar symptoms [58]. Likewise, dysphagia is described in association with anti-Ca, an established cause of cerebellar ataxia [59].

Bickerstaff's brainstem encephalitis overlaps with Guillain-Barre and Miller-Fisher diseases. Around 40—60% of cases may have anti-GQ1b IgG in their serum [60]. In the earliest report, six of seven cases had complete bulbar paralysis. However, milder degrees of dysphagia may be present and overlooked, as one case of silent aspiration is reported. Dietrich-Burns et al. emphasize to be aware of this issue as cognitive impairment may lead to underreporting [61].

There are other conditions with less known underlying autoantibodies. Acute disseminated encephalomyelitis (ADEM) is a mostly monophasic disease, more common among children, that can present with a broad spectrum of symptoms. Dysphagia has been reported as the sole manifestation of the disease in some cases [62]. Although as mentioned earlier, some cases may be anti-MOG positive. Furthermore, chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS) is another similar entity with specific clinical and imaging characteristics. As the main site of involvement is the brainstem, dysphagia could happen in the course of the disease [63].
